Just returning to make sure there is an answer, because I figured it out.
I did a completely fresh umbraco install and hooked to the same database to verify it had to be solution specific.
Our grand plan was to upgrade to 16, let 17 stew for a little bit and then do the jump to 17, so the csproj is set to .net10 …
Returning to .net9 solved the error.
And setting the blank umbraco project to run with .net10 recreated the error 
TLDR; We were running Umbraco 16 on .net10, and apparently that works with everything we’ve tried, except this.