Also set software rendering via the new $GDK_DISABLE variable

GTK 4.14.6+ (Fedora 41+) has moved 'GDK_DEBUG=foo-disable' to
'GDK_DISABLE=foo':

https://gitlab.gnome.org/GNOME/gtk/-/commit/cde094a0dfde3024fae18e0c0d36e7cf5f795dc6

New GTK versions print warnings for the old options:

    Unrecognized value "gl-disable". Try GDK_DEBUG=help
    Unrecognized value "vulkan-disable". Try GDK_DEBUG=help

Author: rustybird

appvm-scripts/etc/profile.d/qubes-gui.csh

@@ -2,6 +2,7 @@ setenv DISPLAY ":0"
 setenv _JAVA_AWT_WM_NONREPARENTING "1"
 if ( -f /var/run/qubes-service/software-rendering )
   setenv GSK_RENDERER "cairo"
+  setenv GDK_DISABLE "gl vulkan"
   setenv GDK_DEBUG "gl-disable vulkan-disable"
   setenv LIBGL_ALWAYS_SOFTWARE "1"
 endif

appvm-scripts/etc/profile.d/qubes-gui.sh

@@ -1,5 +1,7 @@
 export DISPLAY=:0 _JAVA_AWT_WM_NONREPARENTING=1
 if test -f /var/run/qubes-service/software-rendering; then
-  export GSK_RENDERER="cairo" GDK_DEBUG="gl-disable vulkan-disable" \
+  export GSK_RENDERER="cairo" \
+         GDK_DISABLE="gl vulkan" \
+         GDK_DEBUG="gl-disable vulkan-disable" \
          LIBGL_ALWAYS_SOFTWARE=1
 fi