Keyboard & Mouse > Keyboard > Additional layout options > Caps Lock behavior can lock a user out of machine if password contains any lower case letters
- press CAPS LOCK 1. in, so you're typing in UPPERCASE
- select Keyboard & Mouse > Keyboard > Additional layout options > Caps Lock behavior > Make caps lock an additional Super [Really many options in this radio button bank will do]
- try to type in lower case: you can't.
- [optional bonus] wait for screen lock to ask for your password. If it contains lower case letters, you're locked out of that X windows session, as far as I can tell - the only way I found to unset the caps lock was to 'kill -9 -1' from the linux virtual terminal thingy, which burned down x-windows.
gnome-tweaks 3.34.0 / Ubuntu 20.04
Edited by Dave Morse