Crashing when trying to select "qt6gtk2"

[JoeJoeTV]

I installed qt6ct on my Linux Mint 21.3 Cinnamon Machine (based on Ubuntu 22.04), which already has qt5ct configured.

As far as I understand, the existing setting of QT_QPA_PLATFORMTHEME=qt5ct should be fine for qt6ct as well (It is set in a XSession config file).

I also installed qt6gtk2, as I don't know how else to select the GTK platformtheme in qt6ct as nothing showed up for GTK 3 or similar.

After doing this, the option is now showing up in the theme selection dropdown, but as soon as I select it, the program crashes with a segmentation fault and the following output:

Configuration path: "/home/<user>/.config/qt6ct"
Shared QSS paths: QList("/home/<user>/.local/share/qt6ct/qss", "/usr/share/cinnamon/qt6ct/qss", "/usr/share/gnome/qt6ct/qss", "/home/<user>/.local/share/flatpak/exports/share/qt6ct/qss", "/var/lib/flatpak/exports/share/qt6ct/qss", "/usr/local/share/qt6ct/qss", "/usr/share/qt6ct/qss")
Shared color scheme paths: QList("/home/<user>/.local/share/qt6ct/colors", "/usr/share/cinnamon/qt6ct/colors", "/usr/share/gnome/qt6ct/colors", "/home/<user>/.local/share/flatpak/exports/share/qt6ct/colors", "/var/lib/flatpak/exports/share/qt6ct/colors", "/usr/local/share/qt6ct/colors", "/usr/share/qt6ct/colors")

(qt6ct:8137): GLib-GObject-WARNING **: 19:42:39.633: cannot register existing type 'GdkDisplayManager'

(qt6ct:8137): GLib-CRITICAL **: 19:42:39.633: g_once_init_leave: assertion 'result != 0' failed

(qt6ct:8137): GLib-GObject-CRITICAL **: 19:42:39.633: g_object_new_with_properties: assertion 'G_TYPE_IS_OBJECT (object_type)' failed

(qt6ct:8137): GLib-GObject-WARNING **: 19:42:39.633: invalid (NULL) pointer instance

(qt6ct:8137): GLib-GObject-CRITICAL **: 19:42:39.633: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed

(qt6ct:8137): GLib-GObject-WARNING **: 19:42:39.633: invalid (NULL) pointer instance

(qt6ct:8137): GLib-GObject-CRITICAL **: 19:42:39.633: g_signal_connect_data: assertion 'G_TYPE_CHECK_INSTANCE (instance)' failed

(qt6ct:8137): GLib-GObject-WARNING **: 19:42:39.634: cannot register existing type 'GdkDisplay'

(qt6ct:8137): GLib-CRITICAL **: 19:42:39.634: g_once_init_leave: assertion 'result != 0' failed

(qt6ct:8137): GLib-GObject-CRITICAL **: 19:42:39.634: g_type_register_static: assertion 'parent_type > 0' failed

(qt6ct:8137): GLib-CRITICAL **: 19:42:39.634: g_once_init_leave: assertion 'result != 0' failed

(qt6ct:8137): GLib-GObject-CRITICAL **: 19:42:39.634: g_object_new_with_properties: assertion 'G_TYPE_IS_OBJECT (object_type)' failed
Speicherzugriffsfehler (Speicherabzug geschrieben)

This seems to be the issue from #16, but the fix described, so setting the variable in /etc/environment instead of the Xsession config file doesn't fix the issue for me.