GDM wayland login -- display shuts down and is hard to get on again

[Stefan Salewski <mail ssalewski de>]

Since a few months I have GTK 3.22 on my gentoo box, and so I tried to
log in with Wayland support from the graphical GDM display manager.

Works all fine. But one problem is, that the display is shut down after
a few hours sometimes. Initially I had the impression that wayland does
that shut down. But the Gnome screensaver related settings are
disabled, and I never saw that shutdown without wayland.

My current impression is: Monitor shuts down after some hours to save
energy, wayland display driver detects this and shuts down the display
driver in PC to save even more energy. I think that is the right idea,
as the same seems to occur also when I power off the monitor while the
PC is still running.

Getting the display on again is really hard. After much testing a found
one method that works most of the time: Ensure monitor is powered off.
Then press Ctrl-ALT-F3. Wait about one second and switch on the
monitor. Most of the time I can get a visible terminal 3 this way and
can switch back to Gnome GUI with Alt-F2.

May there exist a better solution? A secret wakeup key? Or useful
search terms for search engine? Monitor is connected via USB-C to PC,
PC is Intel NUC skull canyon.

PS: For my previous post, I really forgot to give the explicit link to
the git repository. It is https://github.com/StefanSalewski/gintro

Fortunately that link was contained in the git clone expression
already.