I can confirm that while SubscriptionStoreView(groupID: "...") works fine in Xcode 16.4 (both iPhone Simulator 18.4 and an iPhone with iOS/iPadOS 18.5), it just returns "Subscription Unavailable" when the same code is installed via TestFlight on an iPhone with iOS 18.5. However, SubscriptionStoreView(subscriptions:) does work for the purchase but then subscriptionStatusTask(for:) which only codes in a groupID version does not. So much for attempting to use StoreKit2...

For me, once my app got to TestFlight, it appears that SubscriptionStoreView(groupID:) has issues on iOS 18.5/iPadOS 18.5, while SubscriptionStoreView(subscriptions:) works fine. Under Xcode 16.4, both work fine in the Simulator and on a device.

As of Xcode 16.4, there is limited support for XCTest UI Automation for WatchOS apps (e.g. no recording support). If you remember to add a sleep(1) after every automated app interaction such as .tap(), then you can use XCUIScreen.main.screenshot() and XCTAttachment(screenshot: ..., quality: .original) to automate the collection of screenshots for the AppStore. I have found it useful to use XCTContext.runActivity(named: "...") {} to be able to organize the screenshots reliably.