question

We are migrating our current app from the Google Play Store to the Amazon app store and have run into a snag. For android devices that have Google Play services available we are able to use the advertiser_id as a unique identifier for our own backend system. The problem that we have is that this is not available on Amazon devices and so we have no way to uniquely identify users that register through our app on Fire OS devices, which is not ideal for our situation. The question I have is: is there an Amazon equivalent to the advertiser_id that can be used? Using the Android device id is not a solution anymore as Google is making this obsolete and at some point in the future may be not only deprecated but removed entirely and we only want to maintain one code base for both Android and Amazon. We also don't want to force the user to authenticate through Amazon, as none of our other apps (iOS or Android) have this and we want to maintain the same experience across all platforms. All I am really looking for is a unique identifier that is available on Fire OS devices (besides the Android Device ID, IMEI, or MAC_ADDRESS) the same type that is available on both iOS and Android.