There’s an alpha version of an M1-native PMS. Maybe give it a shot before going a whole different route?
That said, I find Windows 10 Pro to work perfectly fine for my uses. Plex’s very stable on it, and it can run virtual machines natively for other uses if needed. Windows Server 2019 is also a good suggestion (but not cheap unless…) as it gives you a bit more control over updates and doesn’t install the normal junk apps that Windows 10/11 do.
