VS2019 targeting .NET 5 is no longer supported. It might do it, but it's unsupported by Microsoft at this point. Anyone using the .NET 5 runtime (or SDK) is running software that potentially has unfixed or unknown security holes and should stop. If VS2019 cannot target .NET 6, then VS2019 users that want to keep using .NET 5 really should upgrade to VS2022. That's just the hard truth. Lagging behind the way folks did on .NET Framework just isn't really an option with .NET.

It sounds like you're ok with removal of this though, so thanks.

Regarding .NET Standard 2.0 vs. 2.1, targeting 2.1 will only help those on a mono runtime that supports it. But I guess that's a non-empty set because iOS and Android are still based on the mono runtime, right? But don't newer mono runtimes support .NET 6 assemblies too? I'm not sure. If not, then ya, I can look into adding a .NET Standard 2.1 target to the library.

If drops .NET 5 users, it doesn't seem to make much sense.
Unity has started netstandard 2.1 support, so it might be useful as a marker for that, but that would require some other work (including Unity version checks).
I also understood the update policy.
Maybe I was a little too pulled into the image of Microsoft backward compatibility(I liked it)

Thank you.

Remember that PR where we were trying to update unity by a major release or two (#1312)? We had it all going except for a build hang, which never got resolved. I'd love to pull unity forward, add nullable ref annotations everywhere, etc. But we'd need some expert advice to get #1312 merged I think.