README.md: Restructure macOS prep instructions

README.md

@@ -121,34 +121,39 @@ instructions to get started.
 [macOS] Preparing the Platform
 ------------------------------
 
-If you wish to use conda, please see the [section on
-conda](https://doc.sagemath.org/html/en/installation/conda.html) in the Sage
-Installation Manual for guidance instead of the following instructions.
-
-In installations without conda, we strongly recommend to use Homebrew ("the
-missing package manager for macOS") from https://brew.sh/, which provides
-the ``gfortran`` compiler and many libraries.
-
 If your Mac uses the Apple Silicon (M1, arm64) architecture:
 
-- Using Homebrew is required because it provides a version of ``gfortran``
-  with necessary changes for this platform that are not in a released upstream
-  version of GCC. (The ``gfortran`` package that comes with the Sage
-  distribution is not suitable for the M1.)
-
 - If you set up your Mac by transfering files from an older Mac, make sure
   that the directory ``/usr/local`` does not contain an old copy of Homebrew
   (or other software) for the x86_64 architecture that you may have copied
   over.  Note that Homebrew for the M1 is installed in ``/opt/homebrew``, not
   ``/usr/local``.
 
+- If you wish to use conda, please see the [section on
+  conda](https://doc.sagemath.org/html/en/installation/conda.html) in the Sage
+  Installation Manual for guidance.
+
+- Otherwise, using Homebrew ("the missing package manager for macOS") from
+  https://brew.sh/ required because it provides a version of ``gfortran`` with
+  necessary changes for this platform that are not in a released upstream
+  version of GCC. (The ``gfortran`` package that comes with the Sage
+  distribution is not suitable for the M1.)
+
 If your Mac uses the Intel (x86_64) architecture:
 
-- If you do not wish to install Homebrew, you will need to install the latest
-  version of Xcode Command Line Tools.  Open a terminal window and run
-  `xcode-select --install`; then click "Install" in the pop-up window.
-  If the Xcode Command Line Tools are already installed, you may want to
-  check if they need to be updated by typing `softwareupdate -l`.
+- If you wish to use conda, please see the [section on
+  conda](https://doc.sagemath.org/html/en/installation/conda.html) in the Sage
+  Installation Manual for guidance.
+
+- Otherwise, we strongly recommend to use Homebrew ("the missing package
+  manager for macOS") from https://brew.sh/, which provides the ``gfortran``
+  compiler and many libraries.
+
+- Otherwise, if you do not wish to install Homebrew, you will need to install
+  the latest version of Xcode Command Line Tools.  Open a terminal window and
+  run `xcode-select --install`; then click "Install" in the pop-up window.  If
+  the Xcode Command Line Tools are already installed, you may want to check if
+  they need to be updated by typing `softwareupdate -l`.
 
 Instructions to Build from Source
 ---------------------------------