I am using 2021.3.9f1
See if you can build this dll and have unity recognize it on mac
You didn’t link anything besides the documentation on the managed plugins.
Which dll did you want me to build?
edit: never mind I saw there is a tutorial towards the bottom of the page
There are steps on that page for making a dll in msvc, look at the Create a DLL with Visual Studio
section. Just make that super simple dll and see if unity recognizes it as a managed dll