It’s still early and it’s just me working on it so I’m trying to get to stability and then building for (distribute apps to) windows and linux before making all the cli stuff work to let you dev on other OSes.

So “no immediate plans” means check back next year after the 1.0.0 release

What does "not supported" mean?

Does it mean "you can probably get this to work, but it's not my OS so I won't go out of my way to help you" or "the build process depends on something only available on macs"?

There isn't an obvious reason it wouldn't be possible to build on linux or WSL at least on windows.