When I boot Ubuntu, the system has the correct screen resolution until the login screen is displayed. It then temporarily changes to a much lower resolution and restores the original resolution after login.
As far as I understood, the login screen is realized with GDM (used to be LightDM). The posts I read so far recommend to put fix this directly in
/etc/gdm3/Init/Default by adding the appropriate
xrandr command right before
exit 0, in my case
xrandr --output XWAYLAND0 --primary --mode 2560x1440.
After reboot the login screen is still displayed in the wrong resolution or the zoom factor is doubled, which I cannot check.
As the recommended fix does not work: How can I check why it is not working and how can I fix this issue?