> unless you move to the EU or Japan

Not only that, but the "entitlement" (Apple lingo for code-signature flag that grants capabilities) needed to publish a browser effectively requires to be an established company, ensuring hobbyists can't really get there with an open-source project even though the sources of Firefox are available and could technically be ported.

Is this a new rule? I had my own browser published on the App Store about a year ago (as a solo dev).

It goes well beyond requiring an established company. It's so onerous that no company has yet successfully navigated all the gates required - even Google. Apple is maliciously complying with the EU's Digital Rights Act, and many years later, the EU has not concluded its investigations. I am incredibly disappointed.