Okay, now it seems to be “working”.
What did I do:
- Reset to default using the ssdm menu (within system settings)
- Reboot
- Deleted the user manually from the files sddm.conf and kde_settings.conf (as after a reboot I still got an autologin even though the checkbox was not ticked).
- Reboot
This time, the autologin section stuck with the sddm.conf file (maybe due to me setting everything back to default?).
I will reboot several times more in the upcoming days, just to make sure it stays that way.
Best,
Edward