Hi, I have a system with a GeForce 1050 Ti on bullseye.
On this system, if I log in as a regular user and run startx, everything works fine; KDE Plasma comes up and it's all good. But sddm doesn't work. In fact, when it starts, it causes my monitor to go "no signal". Oddly, though, if I can log in blindly, then once I hit enter after putting in my password, KDE will come up and work like it should. I also tried lightdm and xdm. Both of them also had "no signal" when starting. It is using the nouveau driver. There are no errors in Xorg.0.log, journalctl, dmesg, syslog, or the xsession log. lspci doesn't show any other graphics adapter. xrandr on the sddm session shows it detected the appropriate output at the appropriate resolution. Xorg.0.log looks completely appropriate; detecting devices, setting them up, etc. If I boot the same drive on a different box with Intel graphics, sddm works fine. This is a fresh bullseye install. A am utterly baffled; I'd think at least xdm should work! Thanks, John