Am Sonntag 30 August 2020 schrieb Frank Streitz:
> sorry for my bad English but I try to describe my problem so good as
> I can. If I look a video or live stream the screen is after 10
> minutes dark. Only chromecast is able to hold the screen open.
> Firefox or VLC media player can't do this.
> My desktop is mate and the window manager is lightdm and I found no
> place where I can change this from 10 minutes to maybe 2 hours or
> longer. I hope someone can help me. I think this must be a file under
> /etc or something like that.

I had the same problem. This command disables the power saving feature
of the monitor/X-server completely:

$ xset -dpms

You also can set parameters for the time values. See man xset.

This command will show you the current settings in seconds on your
system (600s = 10m):

$ xset q
[…]
DPMS (Energy Star):
  Standby: 600    Suspend: 600    Off: 600
  DPMS is Enabled
  Monitor is On

HTH

Kind regards,
Stefan