Update: I managed to brick my system somehow (display kept restarting whenever any input was made, either mouse move or key press).
The soluton seems to have been to go back to Manjaro for me. It appears that the keyboard is working in Plasma Wayland session, but I do not know why as opposed to my previous EndeavorOS installation.
I will mark this as resolved. Still, I appreciate the help I received here and on Telegram.