SDDM/Plasma gives black screen then returns to greeter after login

Desktop Environments Plasma
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I currently have to switch to a different TTY and run /usr/lib/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland to start the session. Whenever I try logging in through the greeter (whether I choose Wayland or X11, there is no difference) I just see a black screen for a short moment. Immediately after this I am thrown back into the greeter.

Here is my system info (inxi -Fxxc0z): https://0x0.st/Xv6C.txt

My boot log (journalctl -k -b -0): https://0x0.st/XvIr.txt

Journalctl output for SDDM (journalctl --unit=sddm.service): https://0x0.st/XvIi.txt

SDDM config 1 (cat /etc/sddm.conf.d/kde_settings.conf): https://0x0.st/XvIo.txt

SDDM config 2 (cat /etc/sddm.conf.d/10-wayland.conf): https://0x0.st/XvIH.txt

(Note on the 10-wayland.conf file, I have installed both layer-shell-qt and layer-shell-qt5 as detailed in https://wiki.archlinux.org/title/SDDM#Wayland

Pam configs:

cat /etc/pam.d/sddm: https://0x0.st/XvIZ.txt

cat /etc/pam.d/sddm-greeter: https://0x0.st/XvIN.txt

cat /etc/pam.d/sddm-autologin: https://0x0.st/XvIq.txt

I’m at a total loss here. It’s not too difficult to start Plasma over the command line but for it SDDM to just stop working out of the blue is mind boggling. I installed just a couple of weeks ago as well so I don’t have any snapshots to roll back to when everything was working.

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Quick update. I created a new user and was able to log in through the greeter with no problem. I guess my configs are messed up on my original account. Does anyone know how to reset all my Plasma configs to stock? I tried deleting anything KDE/Plasma related from ~/.config but that didn’t fix the issue.

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You did that while the plasma session wasn’t running, I assume?

Note that there may be relevant data in .local as well.

Also possibly stuff left in .cache.

In the absence of fine-grained understanding of the problem, perhaps it’s more realistic to start from scratch and gradually reintroduce the config / user data files you find yourself missing, rather than trying to remove a few files from the … let’s see, I have about 150K between .local and .config, somehow…

Of course it would be much better if somebody could pinpoint where the problem is, but I for one can’t, sadly.

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I have (more-or-less) the same problem. For years plasma (Wayland) has been fine on my laptop but some recent update has screwed things up. I can now only login using XFCE. Choosing Plasma (Wayland) just returns me to the login screen via grub2 (not black screen). I’ve tried removing my plasma-related conf files and followed the advice that @manapropos referenced but no luck. It used to say it couldn’t find the KeyboardButton.qml or the Main.qml file but doesn’t even do that now. The files are in the right place, i.e. /usr/share/sddm/themes/Vivid-SDDM-6. If my issue I have is not relevant to the OP’s could someone let me know?

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~/.config/kwinoutputconfig.json
could cause such issue

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Can’t see anything obvious in kwinoutputconfig.json. Deleting it and rebooting didn’t make a difference.

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I’m pretty sure it’s just an issue with the Vivid-SDDM-6 theme I was using. I had also tried switching my dm to lxdm as it is more suitable for xfce that I am now forced to use. Switching back to sddm gives those errors in the login screen I mentioned above. Apologies if I have hijacked the OP’s thread. It does seem a different issue.

EDIT: Fixed! I ran yay -S --rebuildall $(pacman -Qm) – it rebuilds all AUR packages and on my laptop it took about 2 hours. Requires admin password several times, so don’t look away!

See Undefined symbol when running lookandfeeltool