So I finally got around to do some binary search on the config files, which fortunately didn’t take nearly as long as expected. I narrowed this down to the ~/.config/plasma-org.kde.plasma.desktop-appletsrc
file.
At the very end, it contained the following section:
[ScreenMapping]
itemsOnDisabledScreens=
screenMapping=desktop:/DanMemoDiscordBot/.git/objects/c7,0,11386c69-14f5-424b-afcc-0f50a9b1a329,desktop:/Media/WhatsApp Voice Notes/201933/PTT-20190812-WA0003.opus,1,11386c69-14f5-424b-afcc-0f50a9b1a329,desktop:/Media/WhatsApp Images/Sent/IMG-20221126-WA0004.jpg,1,11386c69-14f5-424b-afcc-0f50a9b1a329, [...]
I shortened the last line here, because it was almost 2 million characters long!
Deleting it and then logging in again fixed the problem.
I have no idea what caused this, and I don’t know whether this was simply too long to handle for the system, or if there was any specific input within that line that broke it.
I kept a copy of the file before I changed it though, and will ask a friend to confirm reproducibility for me.
In any case, do you think this warrants a bug report or something?