Curious how this will play out because they explicitly bypass both Google and Apple
If Fortnite gets banned, they'll stay that way for a long time unless they remove direct payment.
So, you use your browser, login to epicstore with your account, purchase v-bucks at 20% discount and you use those v-bucks in all Epic Games regardless the platform.
Which apps are allowed to open the browser for payments? I don't think even Netflix isn't allowed to do it. They just say "You can't make an account in the app" (paraphrasing) on the sign in page.
Then in the app the Apple/Play payment method is explicitly not discounted.