My Update:
I think I may have been "too late" (as JoJun stated). I followed the instructions at the beginning of this thread (but used 20H2 instead of 21H2 - that's what my PC is running). I also had to update some Dell system files, after which, the PC rebooted. Fingers AND toes were crossed, and all was well.
One ot two days later (when returning to my PC), I see the Upgrade to Windows 11 notice in the bottom right-hand corner of the window. Sure enough, the files had been downloaded to the SoftwareDistribution/Download directory! Argh! I could not find any wuauserv process.
I have since deleted the downloaded files AND emptied the Wastebasket (Recycle Bin).
Any ideas what is triggering the Download and the Upgrade prompt?
Thanks.