A detail I just saw mentioned in a Ars Technica comment about the "alternative app marketplace" part of this.
One of the requirements is:
"Provide Apple a stand-by letter of credit from an A-rated (or equivalent by S&P, Fitch, or Moody’s) financial Institution of €1,000,000 to establish adequate financial means in order to guarantee support for your developers and users."
https://developer.apple.com/support/alternative-app-marketplace-in-the-eu/
This seems like it would make a "FOSS app marketplace" on Apple devices in the EU fairly untenable.