Nothing that I have tried works on android 11 and earlier versions.

Because I tried using different approach but it doesn’t seem to be able to work on android 11 and earlier versions.

Even if is something that can only work on debug mode…

>Solution :

The best way to get unique identifier …

in Android: using unique_identifier to get IMEI

unique_identifier: ^0.0.3
String identifier =await UniqueIdentifier.serial;

in IOS: Apple no longer allows you to retrieve the IMEI or any other device identification