Catalina upgrade stuck on 1 minute remaining

I am trying to upgrade (I think from High Sierra) to Catalina so I can use the latest software. Not sure why it never prompted me to do this, but I checked the system requirements and manually asked for an upgrade on the app store after backing up.

The upgrade went as expected but then hangs on "About a minute remaining". I left it there for about 45 minutes the first time and searched around for solutions. The most common advice is to hold down the power button to force shut down and then it will work upon reboot.

When I did this, it started over at 29 minutes remaining, then got down to 1 minute and did the same thing. Since some people advised trying this multiple times, I have done that, with the same result. The second time I waited a half hour. I would let it go longer, but others are reporting letting it go overnight with no result and there's no longer sound coming from the hard drive indicating it is doing something.

There is no response from the mouse, keyboard, or track pad. Cmd-S does nothing.

Any ideas?