Update:
Even if the Power Manager setting is set to a specific time (I tried 1 hour), it is ignored and the screen blanks anyway at 10 minutes of inactivity. So this setting is broken.
Yes, Mate screensaver is uninstalled. Xscreensaver worked until just recently when I noticed the screen blanking unexpectedly after 10 minutes inactivity.
It’s not a problem with xscreensaver, it’s a problem with the power management which is not working correctly.
Also, I didn’t mention that 2 different computers here are affected.
I had the same problem, that the screen is blanking after 10 minutes no matter what.
I’ve found a solution, at least it works for me.
The screen blanking is done by xorg and not the mate desktop or screensavers.
To disable screenblanking you have to use these commands in the terminal as normal user:
xset dpms 0 0 0
xset -dpms
xset s off
xset s noblank
the only downside is that it will NOT stick, so if you logout or reboot and login again you have to enter those commands again!
the workarround to make it permanent is to go to " Control Center / Startup Applications " and add a entry to put those commands in or create a shell script with the commands to run it each time you log in.
This solved the screenblanking for me, after this the screen remains on if you had NEVER selected in power manager.