After recursive chown of some files to my user in a dir mounted by docker something went wrong and the terminal stopped finding any executables and started giving input/output errors. However, after a hard reboot the system files looked fine: all non-home stuff is owned by the root or a proper system user, all the home files are owned by my user, there are no stray user ids.
Checking with pacman showed that the installed files are fine.
KDE login screen shows the text properly. But when logged in, there is just no text: file manager shows all except the text, no text in settings, no text in Konsole, no text on tooltips, no text in the application launcher, Geany and nvidia-settings launch an oversized window and hang there without showing anything in it, Firefox has all the text but it’s the wrong symbols. Mattermost (an electron app) shows the text correctly, 3D graphics are ok.
Since the login screen and the text terminal login work fine, the problem is probably session-local. Removing files from ~/.config/plasma* doesn’t help. The fc-cache finds the fonts. The session is X11.
Logs of plasmashell look the same as on the system that works.
Is there something to reset? Which files should I compare to the files of a working system?