Yes, I didn't know that I could set "phone-ipad-minimum-performance-a12" when I first developed it, so I was not allowed to add this restriction to the next version (Apple thought it would prevent some users who had downloaded it before from using it), but this restriction still includes the iPhone X series, so I had to remind them in the app users.
I don't know if your app just runs slowly on A12 and lower or if it doesn't run at all. But if it's the latter, perhaps you could detect the UIDevice().type on start and show an alert explaining the situation to the users?
I would also consider putting this information to the very top of the description to try to avoid bad reviews.
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One more feedback: I struggled to find the App Store link in your blog article. I would definitely recommend using Apple's well known marketing badge[0], you can still enhance it with your brand if you want to.
Wow so if I understand correctly: you’ll need to allow downloads from those phones forever, because of a small number of initial downloads? That’s quite an App Store policy
It seems a little strange that it doesn't work for the A12, it could be a performance issue, if the UI doesn't update for a set amount of time, an app will crash out, this can be solved by putting the offending blocking code to a background thread and adding an activity indicator to the main thread until the job is done.
I can't remember what the timeout value is, but say the A12 puts some users on the limit, say due to library size. That could be the issue.
(I'm sorry, I haven't dowloaded the app so I'm guessing on your UI, just know its a fairly common mistake) If you're just putting up a dialog saying "building index", running the code to build the index in the same thread, then dismissing once done, it will lock out UI updates, eventually leading to a crash (I think it's 30 secs for the timeout).
Running code in a high priority background thread with a callback to the main thread is fairly trivial in iOS, there's the fine grained control of GCD, Combine for react like code, and the new async/await pattern.
A UIActivityIndicator can be used to show activity without knowing progress.
