I typed the same thing exactly as you did. I guess Mac kind of counts as Linux as it's just a BSD flavor.
That said, since it implements the BSD syscalls, you can compile virtually any Linux or BSD programs for it easily.
Only downsides are areas where Apple intentionally doesn't match BSD. For instance, the supported OpenGL version is very outdated (although, in practice, there are libraries to translate OpenGL calls to Metal, so it's not that bad).
ReactOS is cool though. Thanks for showing me that. Does it use wine under the covers or is its own thing?
It includes a clean room implementation of the NT kernel, which is quite cool.