On some custom login screens (win7 SDDM theme for eg) - a huge touchscreen keyboard pops up despite not having a touchscreen and having disabled the virtual keyboard in Plasma settings.
Where is it getting activated and why is it specific to some login screens?
I had the same issue.
This solution worked for me: https://www.reddit.com/r/linuxquestions/comments/7k16ve/disable_virtual_keyboard_in_sddm/