Maybe lj could go down the swift backup route where purchases are tied to a Google sign in to avoid play services? You could buy the app from Google play via web, download it via aurora, then validate via in app login.

https://swiftapps.org/faq#whygoogle

Down side is lj would need a verification server (although he has servers for Reddit sync Imgur which he could repurpose for billing).

Disclaimer I am not a dev just a rando lemmy, Lemite? (Idk what to call a lemmy user)