There's a way to find out how many users blocked my notification in the app.
From what I understand reading doc https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/APNSOverview.html#//apple_ref/doc/uid/TP40008194-CH8-SW1
I think the information is shared only between APN server and device. I do not see it accessible (even a simple count) out of APN server.
This may also be useful: https://stackoverflow.com/questions/17262511/how-do-ios-push-notifications-work
