Get Bluetooth battery level in Linux (specifically Ubuntu)

I never noticed, but Ubuntu isnt showing the battery level of connected Bluetooth devices. One needs to enable experimental features in bluetoothd first!

sed -i -r 's/ExecStart=.+/& -E/' /etc/systemd/system/bluetooth.service
systemctl daemon-reload
systemctl restart bluetooth

Running upower -d will show the information:

Device: /org/freedesktop/UPower/devices/headset_dev_AA_AA_AA_BB_BB_BB
  native-path:          /org/bluez/hci0/dev_AA_AA_AA_BB_BB_BB
  model:                Bluetooth Speaker
  serial:               AA:CC:DD:DD:EE:AA
  power supply:         no
  updated:              So 12 Jun 2022 09:06:20 CEST (49 seconds ago)
  has history:          yes
  has statistics:       no
  headset
    warning-level:       none
    percentage:          100%
    icon-name:          'battery-missing-symbolic'