Hello,
on Wayland the system doesn't put the monitor in standby. I set the automatic standby after 10 minutes, but the screen goes black and then immediately wakes up.
I've found this problem on Kubuntu so I thought it was a Ubuntu-related bug, but then I've tested the Fedora Live and I get the same behaviour.

The monitor standby works fine on X11.

Processors: 16 × 12th Gen Intel® Core™ i5-1240P
Memory: 7.3 GiB of RAM
Graphics Processor: Mesa Intel® Graphics
Manufacturer: Intel(R) Client Systems
Product Name: NUC12WSHi5

For future users that may have this problem: in my particular case this problem can be solved selecting the monitor "HDMI" only mode.
The monitor "auto" mode, which automatically selects the source input, for some reason triggers the OS to wake up. If I select the "HDMI" from the monitor sources the monitor standby starts to work fine.
This problem seems to affect only Wayland.

I've tested
- Fedora GNOME Wayland -> the monitor can't go in standby
- Kubuntu Wayland -> the monitor can't go in standby
- Fedora GNOME X11 -> it works fine
- Kubuntu X11 -> it works fine
- Windows 11 -> it works fine