See also yesterday's "Apple’s built-in macOS firewall breaks third-party firewalls" https://obdev.at/blog/apples-built-in-macos-firewall-breaks-...
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I remember back in the day when installing two firewalls or two antivirus programs on Windows would break it, so it will have to be reinstalled. That was 20 years ago, though, one would think we're better at making an OS by now.