After hours of ruling out a mistake on my part, or some change in the compile and hosting options, the only thing left is the tooling. Adjusting my searches slightly and haphazardly, I finally stumbled upon this post <https://github.com/dotnet/sdk/issues/26061> from a few weeks ago.
Some are blaming spaces in paths, maybe, but I'm using SDK 6.0.301 which people are blaming for introducing this problem. There are some angry comments. I downloaded and installed SDK 6.0.5 with 6.0.300, then ran the command dotnet new globaljson --force --sdk-version 6.0.300 which creates a global.json file as suggested. Clean project, rebuild, now it deploys. The hours of suffering I wasted on this is apparently caused by some bug in the donet command, which someone says will be fixed 6.0.2. I'm shitting bricks and spitting chips, because here we are in 2022 and we get error messages like *An error has occured* with not the slightest clue anywhere about what has gone wrong. In the early 1980s we used to get mainframe messages like "JDE833 Program aborted", but even then I could look up the error in a manual and do something useful. Is this progress?! *Greg K*