My laptop's maximum native screen resolution is 3840x2400. I use 1920x1200 for my purposes. The screen looks great except that when I first boot the machine, the login screen is at the 3840x2400 resolution. I checked the /etc/sddm.conf file and synchronized it from the System Settings > Startup and Shutdown > Login Screen menu. However the main login page is still at the highest resolution. How can I explicitly specify the screen resolution?

Same issue. I've tried to do the sync to plasma in settings and most fixes I found on the net use ubuntu based files that don't exist in Neon. I'm not sure where the login screen is getting it's resolution information from or how to change it. It should be a basic setting in the Login Screen (SDDM) settings, like a simple dropdown.

Creating the file dpi.conf in /etc/sddm.conf.d/ and pasting
[X11]
ServerArguments=-nolisten tcp -dpi 192

works for me