Do use iOS 9.3.5 for:
By 2028, Apple is expected to fully deprecate legacy AppStore APIs for iOS versions below 10. At that point, the AppStore on iOS 9.3.5 will likely display a permanent “Cannot Connect to AppStore” error. Devices still in service will become entirely dependent on sideloading via jailbreak or physical file transfer—marking the true end of the iOS 9 era. appstore ios 9.3.5