Configuring the Application Firewall to Allow Airplay Screen Mirroring.

Don't want to poke too many holes in the firewall, just what is needed to make Airplay work.

Are you on a public network and don't have a router? That would be the only reason you need the Firewall turned on.

Is Block all incoming connections set?

There are some other things you can check, here: https://piunikaweb.com/2020/12/25/some-apple-users-facing-airplay-issues-after-macos-big-sur-update-but-we-have-some-possible-workarounds/

I would not consider disabling the firewall an obvious fix

What part of your local network do you need to manage? What devices on your local network do you need to isolate from the others. Do you have an HR computer that you need to keep other devices on your LAN from accessing?

That is the purpose of a Firewall. It is not a security system. It is a internal network management tool to isolate parts of the LAN from other parts of the LAN.

You NAT router already completely isolates your LAN from the rest of the world. Your Firewall is not doing anything but getting in your way. If you think your Firewall is somehow protecting you from the blue meanies on the Internet, you’ve been misinformed.

Anyone that can break through your router will hav no problem getting past the application firewall.

With all due respect, debating the necessity of a firewall does not answer the question.

Maybe not start a debate if that is not what you want.

I offered the best fix that is available to my searching skills. Firewalls, like AV software, cause more problems than they are able to solve.

Well, there seems to be an obvious fix, then.