In sheer frustration I took an older version of Windows 11 (21H2?) and ran a Win10 Pro to Win 11 Pro upgrade through that and it worked fine. This suggests that Microsoft has added, removed, or, more likely, borked something in the current Windows 11 upgrade release.
I know I can run a fresh Win11 Pro install and then reinstall all of my apps. But, seriously, this is a major headache for me, let alone others with more complex installations than my plain vanilla setup.
Microsoft has seriously dropped the credibility ball in recent years. It looks as if they have little to no quality control or testing. And it shows.
I know my “solution” completely ignores security updates. I have no idea how long it will take to update Win11 Pro to the current version, but this did work for me.
By the way. I returned to Win10 Pro as I just couldn’t stand W11 look and feel. Also, Microsoft have removed, relocated, combined or buried many Settings and Control Panel items. Not good.
I think I’ll wait to see if W12 or W13 sorts things out; or, indeed, if Linux can get gaming to function less haphazardly.