Upgrade Mac mini to Big Sur stayed at the Apple screen for an hour with “less than a minute remaining”

The disk space isn’t a problem: 700G available.
it was High Sierra before.
it stays at this “less than a minute remaining” for about an hour now.
what should I do? Hard shut down? Wait for another hour?
the hard disk sounds like churning for now.
kiddo needs to use the computer for school tomorrow. There’s no way the computer is usable at this stage.
how long does it take for people?
Upgrade Mac mini to Big Sur stayed at the Apple screen for an hour with “less than a minute remaining”
 
 
Q