How to change the resolution in SDDM

[petsam]

@ArchStanton

Does anyone have any other suggestions?

You may use an xrandr command to set SDDM display properties.

Change Display priority (KDE/Lightdm)

If you are confident that this command will always work (monitor output names randomly change), then create an executable script with this command, and set it as display-setup-script= value in the [Seats.*] section of /etc/lightdm/lightdm.conf. Test it well, and be prepared for a black screen, just in case… (switch to TTY and rename the file). Plasma has done a lot of progress with multi-monitors, so maybe you try the available options in System Settings/Display, before using the above (if li…

Use SDDM relevant configuration.
Read the tip in this section.