The new desktop arrived Tuesday afternoon.
Windows 11 is not a whole lot different, just time-consuming tweaking it to act like Win 10, which I had already tweaked to act like Win 7.

One all-nighter made the days run together this week.
The only problem was getting the external speakers to work. I had to set my mother's 36" TV up as a 2nd monitor side by side on the old pc, in order to listen to YouTube troubleshooting videos. Gave up and finally contacted Support. The girl was able to take control of the pc remotely and use a mouse as if she were sitting in the same room.
Final diagnosis: failed sound card (?) This doesn't quite make sense because the speakers work through the front headphone jack. I think it's just the connection between the rear ports and the motherboard, which involve some soldered parts. Anyway, they have already scheduled someone to come out to the house Thursday to replace the motherboard.
This pc has only 2 audio ports---green and gray. Most have either 3 or 6. On further checking, this may indicate an older motherboard. I suspected they might try to get rid of outdated parts during Christmas sales. Debated whether to wait until after the new year before ordering for this reason. Flipped a coin. Maybe I'll get 6 audio ports with the new one.