Have you tried using a newer LTS kernel, such as linux66, linux612 or linux618? Even though I’ve never used GNOME, I do see in GDM’s dependencies that polkit is required. As has been mentioned in the Known Issues & Solutions section of every Stable Update announcement since 2026-01-04 (i.e. January), users of kernels earlier than linux66 may encounter problems with polkit:
So, see if booting into a newer kernel resolves the issue. You won’t need to do the other steps recommended in the above post - changing the kernel is all that is needed.
You can install a new kernel via the CLI with the following command (I’ll use linux618 for this example):
sudo mhwd-kernel -i linux618
If booting into the more recent kernel doesn’t fix the issue, then further troubleshooting may be required.
Edit 2026-05-23T10:00:00Z: I’m also wondering about these steps you have done:
GNOME 50 (which all Manjaro branches are currently on) is Wayland-only, so you probably shouldn’t be trying to disable Wayland &/or force an X11 session. A GNOME user may be able to provide more advice regarding this.