I’ve also had Macs online for years without issue.

I guess it only applies to “ephemeral” ports 49152–65535, though I’m not sure what range macOS actually uses. Wikipedia has numbers for Linux and various Windows versions but not macOS: https://en.wikipedia.org/wiki/Ephemeral_port

So does that mean typical desktop usage, like email, web browsing, SSH, etc. would be unaffected? Anyone have any insight on this? I’m not a networking expert myself.

I can’t believe the claim that “everything else dies” when that goes directly against observed reality.

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.

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.