Bluetooth Headset volume too low (only in arch)
VMG's answer is subtly wrong; it will technically work, but it will disable all other plugins than a2dp, meaning bluetooth keyboards/mice/gamepads/etc will stop working, when the only plugin causing issues seems to be one called avrcp.
Edit
/lib/systemd/system/bluetooth.service
and change
ExecStart=/usr/lib/bluetooth/bluetoothd
to
ExecStart=/usr/lib/bluetooth/bluetoothd --noplugin=avrcp
and run
sudo systemctl daemon-reload
sudo systemctl restart bluetooth
My fix on kubuntu:
sudo nano /lib/systemd/system/bluetooth.service
Change
ExecStart=/usr/lib/bluetooth/bluetoothd
to
ExecStart=/usr/lib/bluetooth/bluetoothd --plugin=a2dp
then
sudo systemctl daemon-reload
sudo systemctl restart bluetooth
The effect should be immediate!
Removing AVRCP did not work for me with my WF-1000XM3. What worked was in fact the opposite. I used AVRCP to send volume up commands directly. I used D-Bus to interact with BlueZ following this answer.
In my case the full command was:
dbus-send --print-reply --system --dest=org.bluez /org/bluez/hci0/dev_<mac_address_of_headphones> org.bluez.MediaControl1.VolumeUp