MacOS is not a walled garden any more than Windows is. That’s just iOS/iPadOS.
You can run any software you want on macOS. It doesn’t need to be from the App Store, and it doesn’t need to be notarized by Apple or even signed.
How long that will remain true is an open question. I don’t think they can realistically enforce signing or notarization in the near future. Too much would break.
There are a handful on non-default apps I’ve used across my last 3-4 distros at least:
mpv - the best video player, period. Minimalist UI, maximalist configuration options. I’ve been using it for many years across many OSes and at this point everything else feels wrong.
Geany - My favorite GUI text editor on Linux.
Foliate - the simplest eBook reader I’ve found.
Strawberry - It’s “fine”. Honestly, I’ve never found a music player on Linux that I really liked. I keep falling back to Strawberry because it’s familiar and generally works as expected.
You can run Linux on Mac hardware if that’s what you mean.
But I was talking about the software side, in comparison to Windows.