I see that I have not posted for a while.
I was travelling. The first thing I did on return, was power up my desktop computer. It didn’t power up. It looks like a failure in the power supply. The computer was almost 5 years old, and has been a bit of a lemon all along, so no tears lost on it. I won’t be trying to repair it.
I purchased my UEFI box as a planned replacement for the system that failed. So the UEFI box is now my regular desktop, rather than just a test machine. I learned a few minor things during the transition, so I will post separately on those.