reddit.com/archlinux/disabling_bluetooth_absolute_volume_with_pipewire
create a file:
~/.config/wireplumber/wireplumber.conf.d/80-bluez-properties.conf
With content:
monitor.bluez.properties = { bluez5.enable-hw-volume = false }
Reboot the system or restart wireplumber and pipewire.
Bluetooth configuration — WirePlumber 0.5.2 documentation
Most Bluetooth audio devices do not use ALSA, but bluealsa is available from AUR
GitHub - arkq/bluez-alsa: Bluetooth Audio ALSA Backend