Did you figure out a workaround here? How would it be possible to keep track of users who haven't signed up yet in the "account system"? We are stuck at this very issue ourselves, Apple Support sent me links to Campaigns and asked me to check that out instead.

I am afraid you will have quite the up-hill infront of you. Implementing in-app purchases require 3 things to handle them. The app itself and StoreKit API, setting up In-app purchases in Apple Connect and a separate server (Firebase or other) to handle the receipts and keeping track of who has payed for what.

Having the same issue, please someone please func doSomething(){ print("Thank you!") }