Ok, mein KDE startet wieder. Wie in Thread “Unable to boot after last update” von tommetomme beschrieben, muss der mime.cache neu erstellt werden.
I’ve tracked down the json problem to ~/.local/share/mime/packages
and ~/.local/share/mime/mime.cache. For some reason putting either of
these back into my home folder instantly breaks everything. I’m not,
however, sure if this is the cause of all of my problems. It is a good
start, though. I’m not seeing anything broken by that file and directory
not being there so I’m just going to ignore that for now. I also
managed to rebuild my mime.cache with “mkdir
~/.local/share/mime/packages && update-mime-database
~/.local/share/mime”