adb stands for “Android Debug Bridge” and it’s an Android tool, not specific to Xiaomi.

Why not use Librewolf? Fork of Firefox, hardened and resists fingerprinting. Scores pretty damn well on https://privacytests.org and pairs well with Mull on Android.

AFAIK there are no actively developed Brave forks.

As a heads up, I believe Fennec is the old codebase for Firefox and it’s no longer being actively maintained AFAIK.

Unless, of course, you’re using the Fennec Browser built by F-Droid, which is confusingly based on the new Fenix codebase.