For people like me who thought they have to hack into the Pentagon to spoof their Browser data: you can do that by using chameleon, an extension thats at least in the Firefox add on page
For a while Apple artificially blocked signing in to your Apple ID with physical passkeys (like a Yubikey) on Firefox even though the browser supported it just fine.
Their "iCloud for Windows" browser extensions didn't support Firefox either last time I checked (needed for syncing bookmarks and the password manager).
I dislike Apple more than most people, and they are indeed terrible with standards in general, but with web standards they're doing the world a bit of a favour by pushing WebKit (based on KHTML) on all its users. WebKit is open source and used in for example GNOME Web.
Had it not been for Apple nobody would give a shit about creating websites that work outside of Chrome.