

The first one I think is a fundamental limitation in that display preferences by default is per-user. Maybe this makes it work for you? https://feddit.online/post/1350756/comment/6636228
I don’t really have this problem anymore since I got rid of my projector which advertised a resolution it couldn’t handle. Had to login into the void since the login screen never showed up. Looks like this might be fixable nowadays.
The 24h clock might be similar - check your system-wide locale.
The locale is set to American English but the time format is set to German, something the lock screen can handle but SDDM cannot. I also tried applying the Plasma settings to SDDM a few times but it doesn’t really change anything.









If it’s old enough you can even strip out the entire connectivity module or the physical SIM.