Package issues after update 4.3.51 -> 4.3.66, and some questions

Getting lots of

The type or namespace name ‘Properties’ does not exist in the namespace ‘Unity’ (are you missing an assembly reference?)

All unity packages are up to date, unity version 2020.3.37, A* installed through PM
Am i to assume 2020.3.37 is no longer supported?
The download page for A* 5 states minimum version is 2022, am i royally screwed?
Because i wont update to a newer version in foreseeable future.
If so, do you plan to backport the new features? new local avoidance and so on?
Is there a clear map of which versions require which unity versions?

Version 5’s minimum supported version is 2021.3, though I recommend 2022.2 for the best compatibility and most feature support.
Version 4.3.66 is pretty old by now, unfortunately I do not recall exactly what the minimum supported version of unity was for that. But I think it is unlikely that it was as low as unity 2020.3.

2020.3 is not a version of Unity I’ll be supporting for the newer versions, I’m afraid. It’s used by less than 4% of all users.