During the time of 18.04 it was usually unavoidable for me to actually need to remove mate-power-manager - because it very obviously caused several things, the worst of which was to make the host PC totally unresponsive - which would literally NEVER happen again after it was removed.
Oddly enough - it was possible to replace it with xfce4-power-manager, and that worked pretty well - or just leaving none at all was OK too.
Of course having searched here 1st to see what might have come before, there are many mentions of mate-power-manager being difficult and/or crashy.
Now, using 20.04.3 - this same horrid thing is happening.
My partner's PC was set for the screensaver to start at 40 minutes & the screen to sleep after an hour.
Closely watching it for ~2 hours - the screensaver came on OK, but the screen stayed running & I left it that way when we went to sleep.
During the hours after leaving it untouched - at some point the video vanished, the display's backlight stayed on - and her PC became 100% unresponsive.
I removed mate-power-manager - and Synaptic now shows xfce4-power-manager again, so now it is installed & I'm watching to see how it goes.
Is there some way to make this distro's own power manager better ??
Thanks for any helpful replies !!