SUCCESS
sfc /scannow solved my problem
A number of the commentors in this thread have mentioned using this command without success for them. I decided to try the least drastic method before uninstalling the apparently offending updates of August 9, specifically KB5016616, on my Windows 10 laptop in anticipation of having to do the dreaded system retore (Yes, I have system backups) or, worse yet, a reset and clean install of Windows 10. My computer was working well enough to allow preparation for a short trip I took last week.
After returning, I faced up to fixing things by whatever means. Lo and behold the sfc scan found corrupt system files and replaced them. Everything now works as far as I know. I had been missing the START menu accessed by key or mouse, many Windows accessories such as the snipping tool, access to the Activity Center, Phone Link, the SEARCH function in File Explorer, access to programs unless there were shortcuts on my task bar or desktop or I could find their exe files, and other Windows features. All now work.
Because I had no access to the START menu, I also lost access to finding apps or RUN by simple typing. Fortunately, WINDOWS+X, did bring up a simplified menu of options including Settings, Power Options, and the Windows Power Shell with an option for running it as an Administrator. This access was critical to running the analytical tools without having to start the computer in safe mode.
I followed the instructions from Windows Support.
Windows Support File System Checker
I ran the Deployment Image Servicing and Management (DISM) tool first as required for Windows 8, 8.1, and 10. I then ran sfc /scannow .
The sfc tool reported it had found and replaced corrupted system files. I have not viewed the detail in the CBS log file it created.
As if by magic (AIBM), but actually by the good efforts of the Microsoft programmers and the grace of the Windows deities, I am back in business with relatively little effort. The moral may be, "Always try the simple and minimally intrusive fixes first but have respect for others for which those fixes do not work."
I do not suggest this method will solve everyone's issues. I appreciate the efforts of those much more expert than I am to contribute their experience and knowhow to this forum. With thanks, I am out of here.