Unique way to identify Android devices

Hello there everyone!
I'm trying to integrate an anonymous way to login into my game. Basically I need an identifier that is the same within builds install and for different apps.

I'm working on a gaming franchise so multiple apps will use the same backend for the login
This said, I've researched and:

• Can't use SystemInfo.deviceUniqueIdentifier, due to its link with the sign key (which will change within app)
• MAC Address can't be used, as it now returns a fixed value (same with TelephonyManager IMEI)

This issue seems to be present only in Android. I'm all ears to any solution you may have

Thanks in advance!

 

Update for those who are are seeking for this very problem:

This can be solved by using the very same keystore on apps.
Initially I (wrongly) thought that this would block games to be uploaded to Google Play. Besides that, be aware to any limitations on Android 11+ (they are coming in GREAT numbers).

DISCLAIMER: I'm not related or corroborating with "Don't Kill My App" team, I'm reporting them here with the intent of educational and research purposes

I've faced a lot of problems on Android 11+(shared internal storage, notification services, etc etc), you can find some of good reports here: Don't Kill My App website
I truly recommend deeper investigation towards the problems reported there, as it isn't linear within each brand and model of cellphones

Good luck

All the best,
Breno W.