How can I activate/configure a screensaver in Wayland/GNOME?
So basically I could not find any real wayland-screensaver solution. There was some development and even a small demo of a Wayland screensaver (wscreensaver), but there is not a final program or maybe not even the inital implementation made it into Wayland.
In any case I did not expect that I can (of course) run X.org apps under Wayland using XWayland. Naturally this may not last long into the future, but currently it works. I can run xscreensaver
as it is expected.