Apple bans all such activities, has held the entire app ecosystem and seeks rent. If they think their offering is superior, then they should be OK competing. The fact that they have not opened it up says that they are happy to overcharge.
Remember, competition is always good. Let Stripe and Apple duke it out on payment processing, and let the best one win.
Let games me hosted both on Epic Store and App Store, and let users decide where to download it from.
That will be fair.