It works on Raspberry Pi 3B/Raspberry OS(Buster) with Anker soundcore a3102 BT speakers

[theorbitofmercury]

Option 1:
$ sudo apt install libbluetooth-dev python3-dev
$ pip3 install bluetooth_battery
$ bluetooth_battery XX:XX:...
Battery level for XX:XX:... is 70% (agrees with Android 11)

Incidentally does it only report in jumps of 10%? After some time it was reporting 60% but I never saw anything in-between. I had a look at your code but did not see anything to account for this so maybe its a function of the BT device?

Many thanks