Well, you need to install the app at least once, no need to give it full permissions. You might also use a burner device. Once your device is paired, you can remove the app and go to fetch the key.

Search for huami-token on github or for Huafetcher (android version of the same) on Codeberg.

And read our wiki

Disclaimer: I did the Kivy wrapping of huami-token for Android.