I think there’s two official ways of going about this:
1. Publish an alternative app marketplace in the European Union under Apple’s draconian rules. https://developer.apple.com/documentation/appdistribution/creating-an-alternative-app-marketplace/
2. Make nostr:npub10r8xl2njyepcw2zwv3a6dyufj4e4ajx86hz6v4ehu4gnpupxxp7stjt2p8 also a web client and have the download links go to the official App Store or TestFlight.