Changes
Version 1.0.80 of the Xamarin Android app based the device ID onto the [https://developer.android.com/reference/android/provider/Settings.Secure#ANDROID_ID ANDROID_ID (SSAID)], in the same way to how the native Android client does it. This also removed the need for the <code>READ_PHONE_STATE</code> permission. This method now also works for Android 10+, even for unenrolled devices.
=== iOS ===
On iOS, the application makes use of the [https://developer.apple.com/documentation/uikit/uidevice/1620059-identifierforvendor| identifierForVendor]. This is a GUID uniquely identifying a device to an app vendor.