Instead of a login screen I only see a giant brown keyboard. It is still possible to enter a password and login. I can even remove the keyboard with Esc (I think) but only blank screen shows. When I use Breeze as my login screen theme however everything is fine, so it must relate to the theme, but it is broken in any other theme I've tried (e.g., sweet).
I'm using kubuntu 18.04, freshly installed yesterday.
p.s. The title is a bit misleading but I think it might be a helpful description for future users that have the same issue.