I installed KDE Plasma Workspace with a Fedora 37 network installation on my System76 Gazelle a few months ago (dual-booting with Pop!_OS on a separate SSD). I’ve had a number of issues with KDE which I won’t go into here, and although I’ve also installed Xfce, I can’t switch to it because sddm no longer gives a selection for user or session – it comes up with a white screen that has a password prompt in the center. From there, I can successfully log in as that one user, but logging out or re-booting just brings me back to the white password screen.
I’m not familiar enough with sddm to know how to troubleshoot this. FWIW, I’ve tried clearing out /var/lib/sddm/, but that hasn’t helped. Google hasn’t helped find anyone reporting this issue.
Not sure it matters, but the session that starts appears to be Wayland rather than X. Also, I originally configured the machine in “hybrid” graphics mode (nVidia + Intel graphics) but later switched to Intel-only. I don’t remember when this symptom started, so I’m not sure whether there’s any correlation between them. I’ll try switching back to see if it makes a difference.