I'm working on 2 video games built using the Unity3D game engine (game-1 and game-2).
For iOS, I used advertisingIdentifier which holds the same value across all the apps developed by the same developer. In other words, the advertisingIdentifier variable in game-1 holds the exact value stored in the advertisingIdentifier variable in game-2.
I use this unique id per device for different features. For example, I limit the user's account to be logged in to up to 3 different devices only but the user can log in to unlimited games on the same account (game-1, game-2, game-3...)
For Android, I didn't find any similar Identifier. I tried to use uuid which turned out to be unique per app (game-1 and game-2 installed on the same device don't have the same uuid). I also tried to use MAC addresses which weren't stable at all, some devices support it but not all devices.
Is there any solution to this problem? Even if it depends on a cloud service (Firebase for example) or anything similar, it's fine.