Thank you so much for the help. This was the fix for me. I had the plasma 5 theme and needed the plasma 6 one. Also the last tip about themes is very appreciated and will be considered. <3

I'm running Fedora 40 with kde plasma DE if it helps any

I've tried switching lock screen themes and gotten it to work temporarily but it goes back to default with that red error text on a reboot.

I have indeed tried that but it hasn't worked.

i do have encryption enabled as security was one of the main reasons i moved to linux. however im going to keep autologin disabled as i like requiring a password after waking from sleep.