In my computer, GDM is using wayland in its login screen. I have observed that while in the login screen the screen saver never activates and the monitor stays on all the time. It worked fine with Ubuntu 16.04, that used Xorg. Once logged on, the screen saver works fine both in Xorg and Wayland sessions.
Disabling wayland in /etc/gdm3/custom.conf solves the problem, but then I can not choose to start the session in wayland mode anymore.
Is there a way to configure the screen saver for the gdm login screen when in wayland mode?