diff --git a/src/sage/features/__init__.py b/src/sage/features/__init__.py
index cb2e2a085c3..fc60ac746b7 100644
--- a/src/sage/features/__init__.py
+++ b/src/sage/features/__init__.py
@@ -52,6 +52,19 @@
 As can be seen above, features try to produce helpful error messages.
 """
 
+# *****************************************************************************
+#       Copyright (C) 2016      Julian Rüth
+#                     2018      Jeroen Demeyer
+#                     2018      Timo Kaufmann
+#                     2019-2022 Matthias Koeppe
+#                     2021      Kwankyu Lee
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from __future__ import annotations
 
 import os
diff --git a/src/sage/features/all.py b/src/sage/features/all.py
index 2ec0c267b83..19eabe60126 100644
--- a/src/sage/features/all.py
+++ b/src/sage/features/all.py
@@ -2,6 +2,15 @@
 Enumeration of all defined features
 """
 
+# *****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 def all_features():
     r"""
     Return an iterable of all features.
diff --git a/src/sage/features/bliss.py b/src/sage/features/bliss.py
index e8efd3e8f97..aeadedfebff 100644
--- a/src/sage/features/bliss.py
+++ b/src/sage/features/bliss.py
@@ -1,7 +1,18 @@
-# -*- coding: utf-8 -*-
 r"""
 Features for testing the presence of ``bliss``
 """
+
+# *****************************************************************************
+#       Copyright (C) 2016 Julian Rüth
+#                     2018 Jeroen Demeyer
+#                     2021 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import CythonFeature, PythonModule
 from .join_feature import JoinFeature
 
diff --git a/src/sage/features/cddlib.py b/src/sage/features/cddlib.py
index 59a72a2120f..5badbd251c0 100644
--- a/src/sage/features/cddlib.py
+++ b/src/sage/features/cddlib.py
@@ -1,6 +1,16 @@
 r"""
 Feature for testing the presence of ``cddlib``
 """
+
+# *****************************************************************************
+#       Copyright (C) 2022 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import Executable
 
 
diff --git a/src/sage/features/csdp.py b/src/sage/features/csdp.py
index e86ec415d09..9c04779558c 100644
--- a/src/sage/features/csdp.py
+++ b/src/sage/features/csdp.py
@@ -3,6 +3,18 @@
 Feature for testing the presence of ``csdp``
 """
 
+# *****************************************************************************
+#       Copyright (C) 2016 Julian Rüth
+#                     2018 Jeroen Demeyer
+#                     2019 David Coudert
+#                     2021 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 import os
 import re
 import subprocess
diff --git a/src/sage/features/cython.py b/src/sage/features/cython.py
index f537843f4f4..8f03155ac2f 100644
--- a/src/sage/features/cython.py
+++ b/src/sage/features/cython.py
@@ -1,8 +1,16 @@
-# -*- coding: utf-8 -*-
 r"""
 Features for testing the presence of ``cython``
 """
 
+# *****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import CythonFeature
 
 
diff --git a/src/sage/features/databases.py b/src/sage/features/databases.py
index d1e77a8ff32..7fa05ca099a 100644
--- a/src/sage/features/databases.py
+++ b/src/sage/features/databases.py
@@ -1,8 +1,21 @@
-# -*- coding: utf-8 -*-
 r"""
 Features for testing the presence of various databases
 """
 
+# *****************************************************************************
+#       Copyright (C) 2016      Julian Rüth
+#                     2018-2019 Jeroen Demeyer
+#                     2018      Timo Kaufmann
+#                     2020-2022 Matthias Koeppe
+#                     2020-2022 Sebastian Oehms
+#                     2021      Kwankyu Lee
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 
 from . import StaticFile, PythonModule
 from sage.env import (
diff --git a/src/sage/features/dvipng.py b/src/sage/features/dvipng.py
index 44ef6c7074a..281084a6e72 100644
--- a/src/sage/features/dvipng.py
+++ b/src/sage/features/dvipng.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 r"""
 Feature for testing the presence of ``dvipng``
 """
diff --git a/src/sage/features/ffmpeg.py b/src/sage/features/ffmpeg.py
index bb708478251..681af26494c 100644
--- a/src/sage/features/ffmpeg.py
+++ b/src/sage/features/ffmpeg.py
@@ -1,9 +1,8 @@
-# -*- coding: utf-8 -*-
 r"""
 Feature for testing the presence of ``ffmpeg``
 """
 # ****************************************************************************
-#       Copyright (C) 2018 Sebastien Labbe <slabqc@gmail.com>
+#       Copyright (C) 2018-2022 Sebastien Labbe <slabqc@gmail.com>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
diff --git a/src/sage/features/gap.py b/src/sage/features/gap.py
index 20add30c114..67c905a35c3 100644
--- a/src/sage/features/gap.py
+++ b/src/sage/features/gap.py
@@ -1,9 +1,18 @@
-# -*- coding: utf-8 -*-
 r"""
 Features for testing the presence of GAP packages
 """
+# *****************************************************************************
+#       Copyright (C) 2016 Julian Rüth
+#                     2018 Jeroen Demeyer
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
 
-from . import Feature, FeatureTestResult
+from . import Feature, FeatureTestResult, PythonModule
+from .join_feature import JoinFeature
 
 
 class GapPackage(Feature):
@@ -48,3 +57,34 @@ def _is_present(self):
         else:
             return FeatureTestResult(self, False,
                     reason="`{command}` evaluated to `{presence}` in GAP.".format(command=command, presence=presence))
+
+
+class sage__libs__gap(JoinFeature):
+    r"""
+    A :class:`sage.features.Feature` describing the presence of :mod:`sage.libs.gap`
+    (the library interface to GAP) and :mod:`sage.interfaces.gap` (the pexpect
+    interface to GAP). By design, we do not distinguish between these two, in order
+    to facilitate the conversion of code from the pexpect interface to the library
+    interface.
+
+    EXAMPLES::
+
+        sage: from sage.features.gap import sage__libs__gap
+        sage: sage__libs__gap().is_present()                       # optional - sage.libs.gap
+        FeatureTestResult('sage.libs.gap', True)
+    """
+    def __init__(self):
+        r"""
+        TESTS::
+
+            sage: from sage.features.gap import sage__libs__gap
+            sage: isinstance(sage__libs__gap(), sage__libs__gap)
+            True
+        """
+        JoinFeature.__init__(self, 'sage.libs.gap',
+                             [PythonModule('sage.libs.gap.libgap'),
+                              PythonModule('sage.interfaces.gap')])
+
+
+def all_features():
+    return [sage__libs__gap()]
diff --git a/src/sage/features/gfan.py b/src/sage/features/gfan.py
index 6551ca5340c..d9a74db9e1b 100644
--- a/src/sage/features/gfan.py
+++ b/src/sage/features/gfan.py
@@ -2,6 +2,15 @@
 Features for testing the presence of ``gfan``
 """
 
+# *****************************************************************************
+#       Copyright (C) 2022 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import Executable
 
 
diff --git a/src/sage/features/graph_generators.py b/src/sage/features/graph_generators.py
index 0ecd63bad76..3d484c59f6b 100644
--- a/src/sage/features/graph_generators.py
+++ b/src/sage/features/graph_generators.py
@@ -1,8 +1,20 @@
-# -*- coding: utf-8 -*-
 r"""
 Features for testing the presence of various graph generator programs
 """
 
+# *****************************************************************************
+#       Copyright (C) 2016 Julian Rüth
+#                     2018 Jeroen Demeyer
+#                     2019 Frédéric Chapoton
+#                     2021 Matthias Koeppe
+#                     2021 Kwankyu Lee
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 import os
 import subprocess
 
diff --git a/src/sage/features/graphviz.py b/src/sage/features/graphviz.py
index 0a0c8ba88e9..2105eda9d8c 100644
--- a/src/sage/features/graphviz.py
+++ b/src/sage/features/graphviz.py
@@ -1,9 +1,10 @@
-# -*- coding: utf-8 -*-
 r"""
 Features for testing the presence of ``graphviz``
 """
+
 # ****************************************************************************
 #       Copyright (C) 2018 Sebastien Labbe <slabqc@gmail.com>
+#                     2021 Matthias Koeppe
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -11,6 +12,7 @@
 # (at your option) any later version.
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
+
 from . import Executable
 from .join_feature import JoinFeature
 
diff --git a/src/sage/features/igraph.py b/src/sage/features/igraph.py
index 04ac4efbb54..6bb83294a95 100644
--- a/src/sage/features/igraph.py
+++ b/src/sage/features/igraph.py
@@ -1,6 +1,17 @@
 r"""
 Check for igraph
 """
+
+# ****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# ****************************************************************************
+
 from . import PythonModule
 from .join_feature import JoinFeature
 
diff --git a/src/sage/features/imagemagick.py b/src/sage/features/imagemagick.py
index 59e35cb5a7a..b7aa3aeb9a2 100644
--- a/src/sage/features/imagemagick.py
+++ b/src/sage/features/imagemagick.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 r"""
 Feature for testing the presence of ``imagemagick``
 
@@ -7,8 +6,9 @@
 ``identify``, ``composite``, ``montage``, ``compare``, etc. could be also
 checked in this module.
 """
+
 # ****************************************************************************
-#       Copyright (C) 2018 Sebastien Labbe <slabqc@gmail.com>
+#       Copyright (C) 2018-2022 Sebastien Labbe <slabqc@gmail.com>
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
diff --git a/src/sage/features/interfaces.py b/src/sage/features/interfaces.py
index b77c2cc4f88..e31e7b72d61 100644
--- a/src/sage/features/interfaces.py
+++ b/src/sage/features/interfaces.py
@@ -1,6 +1,17 @@
 r"""
 Features for testing whether interpreter interfaces are functional
 """
+
+# ****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# ****************************************************************************
+
 import importlib
 
 from . import Feature, FeatureTestResult, PythonModule
diff --git a/src/sage/features/internet.py b/src/sage/features/internet.py
index 6e800120828..f1eb000fe92 100644
--- a/src/sage/features/internet.py
+++ b/src/sage/features/internet.py
@@ -2,6 +2,16 @@
 Feature for testing if the Internet is available
 """
 
+# ****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# ****************************************************************************
+
 from . import Feature, FeatureTestResult
 
 
diff --git a/src/sage/features/join_feature.py b/src/sage/features/join_feature.py
index 94830eead1e..d02ad669833 100644
--- a/src/sage/features/join_feature.py
+++ b/src/sage/features/join_feature.py
@@ -2,6 +2,17 @@
 Join features
 """
 
+# ****************************************************************************
+#       Copyright (C) 2021-2022 Matthias Koeppe
+#                     2021-2022 Kwankyu Lee
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# ****************************************************************************
+
 from . import Feature, FeatureTestResult
 
 
diff --git a/src/sage/features/kenzo.py b/src/sage/features/kenzo.py
index df2e658e975..655602427b8 100644
--- a/src/sage/features/kenzo.py
+++ b/src/sage/features/kenzo.py
@@ -1,8 +1,20 @@
-# -*- coding: utf-8 -*-
 r"""
 Feature for testing the presence of ``kenzo``
 """
 
+# ****************************************************************************
+#       Copyright (C) 2020 Travis Scrimshaw
+#                     2021 Matthias Koeppe
+#                     2021 Michael Orlitzky
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# ****************************************************************************
+
+
 from . import Feature, FeatureTestResult
 
 class Kenzo(Feature):
diff --git a/src/sage/features/latex.py b/src/sage/features/latex.py
index 02bcb57a0ca..1b01db39f67 100644
--- a/src/sage/features/latex.py
+++ b/src/sage/features/latex.py
@@ -1,9 +1,12 @@
-# -*- coding: utf-8 -*-
 r"""
 Features for testing the presence of ``latex`` and equivalent programs
 """
+
 # ****************************************************************************
 #       Copyright (C) 2021 Sebastien Labbe <slabqc@gmail.com>
+#                     2021 Matthias Koeppe
+#                     2022 Kwankyu Lee
+#                     2022 Sebastian Oehms
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
diff --git a/src/sage/features/latte.py b/src/sage/features/latte.py
index 6202152501f..e88752bd561 100644
--- a/src/sage/features/latte.py
+++ b/src/sage/features/latte.py
@@ -1,7 +1,20 @@
-# -*- coding: utf-8 -*-
 r"""
 Features for testing the presence of ``latte_int``
 """
+
+# ****************************************************************************
+#       Copyright (C) 2018 Vincent Delecroix
+#                     2019 Frédéric Chapoton
+#                     2021 Matthias Koeppe
+#                     2021 Kwankyu Lee
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 2 of the License, or
+# (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# ****************************************************************************
+
 from . import Executable
 from .join_feature import JoinFeature
 
diff --git a/src/sage/features/lrs.py b/src/sage/features/lrs.py
index d7b15fbcdd6..501d1d371e7 100644
--- a/src/sage/features/lrs.py
+++ b/src/sage/features/lrs.py
@@ -3,6 +3,19 @@
 Feature for testing the presence of ``lrslib``
 """
 
+# *****************************************************************************
+#       Copyright (C) 2016      Julian Rüth
+#                     2018      Jeroen Demeyer
+#                     2021-2022 Matthias Koeppe
+#                     2021      Kwankyu Lee
+#                     2022      Sébastien Labbé
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 import subprocess
 
 from . import Executable, FeatureTestResult
diff --git a/src/sage/features/mcqd.py b/src/sage/features/mcqd.py
index 131b175aabc..faf7ace441d 100644
--- a/src/sage/features/mcqd.py
+++ b/src/sage/features/mcqd.py
@@ -2,6 +2,15 @@
 Features for testing the presence of ``mcqd``
 """
 
+# *****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import PythonModule
 from .join_feature import JoinFeature
 
diff --git a/src/sage/features/meataxe.py b/src/sage/features/meataxe.py
index d3f7fce200e..78de1bdfe03 100644
--- a/src/sage/features/meataxe.py
+++ b/src/sage/features/meataxe.py
@@ -2,6 +2,17 @@
 Feature for testing the presence of ``meataxe``
 """
 
+# *****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#                     2021 Kwankyu Lee
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
+
 from . import PythonModule
 from .join_feature import JoinFeature
 
diff --git a/src/sage/features/mip_backends.py b/src/sage/features/mip_backends.py
index 477d88efabf..d276e25abe8 100644
--- a/src/sage/features/mip_backends.py
+++ b/src/sage/features/mip_backends.py
@@ -2,6 +2,16 @@
 Features for testing the presence of :class:`MixedIntegerLinearProgram` backends
 """
 
+# *****************************************************************************
+#       Copyright (C) 2021-2022 Matthias Koeppe
+#                     2021      Kwankyu Lee
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import Feature, PythonModule, FeatureTestResult
 from .join_feature import JoinFeature
 
diff --git a/src/sage/features/msolve.py b/src/sage/features/msolve.py
index a7c7d5441b7..557632ff500 100644
--- a/src/sage/features/msolve.py
+++ b/src/sage/features/msolve.py
@@ -9,6 +9,15 @@
     - :mod:`sage.rings.polynomial.msolve`
 """
 
+# *****************************************************************************
+#       Copyright (C) 2022 Marc Mezzarobba
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 import subprocess
 from . import Executable
 from . import FeatureTestResult
diff --git a/src/sage/features/nauty.py b/src/sage/features/nauty.py
index 86683eb29df..f3df59f4a9c 100644
--- a/src/sage/features/nauty.py
+++ b/src/sage/features/nauty.py
@@ -2,6 +2,15 @@
 Features for testing the presence of nauty executables
 """
 
+# *****************************************************************************
+#       Copyright (C) 2022 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from sage.env import SAGE_NAUTY_BINS_PREFIX
 
 from . import Executable
diff --git a/src/sage/features/normaliz.py b/src/sage/features/normaliz.py
index 5c3ab4255f3..acf8c9242c1 100644
--- a/src/sage/features/normaliz.py
+++ b/src/sage/features/normaliz.py
@@ -1,6 +1,16 @@
 r"""
 Feature for testing the presence of ``pynormaliz``
 """
+
+# *****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import PythonModule
 from .join_feature import JoinFeature
 
diff --git a/src/sage/features/pandoc.py b/src/sage/features/pandoc.py
index 0a2bbcdacdb..a00a2b6f8e4 100644
--- a/src/sage/features/pandoc.py
+++ b/src/sage/features/pandoc.py
@@ -4,6 +4,7 @@
 """
 # ****************************************************************************
 #       Copyright (C) 2018 Thierry Monteil <sage!lma.metelu.net>
+#                     2021 Matthias Koeppe
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
diff --git a/src/sage/features/pdf2svg.py b/src/sage/features/pdf2svg.py
index 9de3fb3cfd6..2b60574fe85 100644
--- a/src/sage/features/pdf2svg.py
+++ b/src/sage/features/pdf2svg.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 r"""
 Feature for testing the presence of ``pdf2svg``
 """
diff --git a/src/sage/features/phitigra.py b/src/sage/features/phitigra.py
index f792d7b47cd..60ef8f46dde 100644
--- a/src/sage/features/phitigra.py
+++ b/src/sage/features/phitigra.py
@@ -1,6 +1,16 @@
 r"""
 Check for phitigra
 """
+
+# *****************************************************************************
+#       Copyright (C) 2022 Jean-Florent Raymond
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import PythonModule
 
 
diff --git a/src/sage/features/pkg_systems.py b/src/sage/features/pkg_systems.py
index 5e31ec9f66d..334f8378050 100644
--- a/src/sage/features/pkg_systems.py
+++ b/src/sage/features/pkg_systems.py
@@ -1,6 +1,16 @@
 r"""
 Features for testing the presence of package systems
 """
+
+# *****************************************************************************
+#       Copyright (C) 2021-2022 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import Feature
 
 
diff --git a/src/sage/features/polymake.py b/src/sage/features/polymake.py
index 579951c047f..6168c6c9978 100644
--- a/src/sage/features/polymake.py
+++ b/src/sage/features/polymake.py
@@ -1,6 +1,16 @@
 r"""
 Feature for testing the presence of the Python interface to polymake
 """
+
+# *****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import PythonModule
 from .join_feature import JoinFeature
 
diff --git a/src/sage/features/poppler.py b/src/sage/features/poppler.py
index 1b0379bc0d2..b8f8586e7f5 100644
--- a/src/sage/features/poppler.py
+++ b/src/sage/features/poppler.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 r"""
 Check for poppler features
 
diff --git a/src/sage/features/rubiks.py b/src/sage/features/rubiks.py
index b418c1571cb..b9bd2f126f7 100644
--- a/src/sage/features/rubiks.py
+++ b/src/sage/features/rubiks.py
@@ -1,14 +1,17 @@
-# -*- coding: utf-8 -*-
 r"""
 Features for testing the presence of ``rubiks``
 """
 # ****************************************************************************
+#       Copyright (C) 2020      John H. Palmieri
+#                     2021-2022 Matthias Koeppe
+#
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation, either version 2 of the License, or
 # (at your option) any later version.
 #                  https://www.gnu.org/licenses/
 # ****************************************************************************
+
 from sage.env import RUBIKS_BINS_PREFIX
 
 from . import Executable
diff --git a/src/sage/features/sagemath.py b/src/sage/features/sagemath.py
index 3cb66162f07..fd090764b44 100644
--- a/src/sage/features/sagemath.py
+++ b/src/sage/features/sagemath.py
@@ -1,6 +1,17 @@
 r"""
 Features for testing the presence of Python modules in the Sage library
 """
+
+# *****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#                     2021 Kwankyu Lee
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import PythonModule, StaticFile
 from .join_feature import JoinFeature
 
diff --git a/src/sage/features/singular.py b/src/sage/features/singular.py
index 610e195c641..c3bd3b6be03 100644
--- a/src/sage/features/singular.py
+++ b/src/sage/features/singular.py
@@ -1,7 +1,18 @@
 r"""
 Features for testing the presence of Singular
 """
-from . import Executable
+
+# *****************************************************************************
+#       Copyright (C) 2022-2023 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
+from . import Executable, PythonModule
+from .join_feature import JoinFeature
 from sage.env import SINGULAR_BIN
 
 
@@ -25,3 +36,35 @@ def __init__(self):
         """
         Executable.__init__(self, "singular", SINGULAR_BIN,
                             spkg='singular')
+
+
+class sage__libs__singular(JoinFeature):
+    r"""
+    A :class:`sage.features.Feature` describing the presence of :mod:`sage.libs.singular`
+    (the library interface to Singular) and :mod:`sage.interfaces.singular` (the pexpect
+    interface to Singular). By design, we do not distinguish between these two, in order
+    to facilitate the conversion of code from the pexpect interface to the library
+    interface.
+
+    EXAMPLES::
+
+        sage: from sage.features.singular import sage__libs__singular
+        sage: sage__libs__singular().is_present()                       # optional - sage.libs.singular
+        FeatureTestResult('sage.libs.singular', True)
+    """
+    def __init__(self):
+        r"""
+        TESTS::
+
+            sage: from sage.features.singular import sage__libs__singular
+            sage: isinstance(sage__libs__singular(), sage__libs__singular)
+            True
+        """
+        JoinFeature.__init__(self, 'sage.libs.singular',
+                             [PythonModule('sage.libs.singular.singular'),
+                              PythonModule('sage.interfaces.singular')])
+
+
+def all_features():
+    return [Singular(),
+            sage__libs__singular()]
diff --git a/src/sage/features/sphinx.py b/src/sage/features/sphinx.py
index d29de3f34f4..44283765fd1 100644
--- a/src/sage/features/sphinx.py
+++ b/src/sage/features/sphinx.py
@@ -1,6 +1,16 @@
 r"""
 Check for Sphinx
 """
+
+# *****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import PythonModule
 
 
diff --git a/src/sage/features/standard.py b/src/sage/features/standard.py
new file mode 100644
index 00000000000..f48f47f2614
--- /dev/null
+++ b/src/sage/features/standard.py
@@ -0,0 +1,35 @@
+r"""
+Check for various standard packages (for modularized distributions)
+
+These features are provided by standard packages in the Sage distribution.
+"""
+
+# *****************************************************************************
+#       Copyright (C) 2023 Matthias Koeppe
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
+from . import PythonModule
+from .join_feature import JoinFeature
+
+
+def all_features():
+    return [PythonModule('cvxopt', spkg='cvxopt'),
+            PythonModule('fpylll', spkg='fpylll'),
+            JoinFeature('ipython', (PythonModule('IPython'),), spkg='ipython'),
+            JoinFeature('lrcalc_python', (PythonModule('lrcalc'),), spkg='lrcalc_python'),
+            PythonModule('mpmath', spkg='mpmath'),
+            PythonModule('networkx', spkg='networkx'),
+            PythonModule('numpy', spkg='numpy'),
+            PythonModule('pexpect', spkg='pexpect'),
+            JoinFeature('pillow', (PythonModule('PIL'),), spkg='pillow'),
+            JoinFeature('pplpy', (PythonModule('ppl'),), spkg='pplpy'),
+            PythonModule('primecountpy', spkg='primecountpy'),
+            PythonModule('ptyprocess', spkg='ptyprocess'),
+            PythonModule('requests', spkg='requests'),
+            PythonModule('scipy', spkg='scipy'),
+            PythonModule('sympy', spkg='sympy')]
diff --git a/src/sage/features/tdlib.py b/src/sage/features/tdlib.py
index ff38f6e23a5..afde40f7de7 100644
--- a/src/sage/features/tdlib.py
+++ b/src/sage/features/tdlib.py
@@ -2,6 +2,16 @@
 Features for testing the presence of ``tdlib``
 """
 
+# *****************************************************************************
+#       Copyright (C) 2021 Matthias Koeppe
+#                     2021 Kwankyu Lee
+#
+#  Distributed under the terms of the GNU General Public License (GPL)
+#  as published by the Free Software Foundation; either version 2 of
+#  the License, or (at your option) any later version.
+#                  https://www.gnu.org/licenses/
+# *****************************************************************************
+
 from . import PythonModule
 from .join_feature import JoinFeature