Hello:

On 7 Nov 2025 at 10:36, Bob Bowles wrote:

> ... 10-minute mark the screen went blank. Then I moved the
> mouse, and the screen came back, just like a screensaver, Except I
> don't have a screensaver ...
Interesting indeed.

Like I may have mentioned I run Devuan Daedalus with the XFCE desktop
and SLiM, this with two NVidia cards running three monitors using the
nouveau drivers for a 3840x1024 desktop.

The layout is as follows: the left monitor is the primary one,
sharing the first Nvidia card with the right monitor, the centre
monitor running off the second card.

Even though I made sure that there were no XFCE (or other) power
management applicatios running, after some time (never timed it) the
left and right monitors will go off, just like yours ie: screen saver
mode.

Moving the mouse brings them back on, the difference being that I do
not get logged off.

It is rather annoying because those two monitors are old (but
perfectly working) 19" Samsing SyncMaster 940n which use FL lamps.

FL lamps are affected by coldish room temperatures in wintertime and
as a result the screen is dimmed while thay warm up, particulalry if
they have over 34K hours on them like these. 8^°

I never bothered to research further on how to turn this 'feature'
off as I expect the FL lamps will last a bit longer by keeping it as
it is.

SLiM seems to be off the hook and maybe XFCE too as this happens even
without my being logged in.

ie: bringing my system up and going to make my morning espresso while
it boots. If enough time has passed, on coming back to my desk I will
need to move the mouse to get the log-in screen on the primary
monitor.

Note that the centre monitor does *not* get put to sleep.

It would seem (?) that you may be experiencing the same thing in your
setup.

Best,

A.