I reinstall kubuntu-desktop (because I had issue with it) and after that I ran into of a problem with font size. All fonts on the screen are very big! I changed font size in the Settings - Fonts - Fonts - Adjust All Fonts. It works fine, but not for login screen! Login screen have very big elements and text! In my opinion it's can be two issue: wrong resolution of the login screen or wrong font size. Could you please ask how can I change resolution or font size on the sddm login screen?