I recommend to use for this Pipewire. On pulseaudio not tested this method.

Add new file

sudo subl /etc/wireplumber/wireplumber.conf.d/50-bluez.conf

With

monitor.bluez.properties = {
    bluez5.enable-msbc = true
}

Then

systemctl --user restart pipewire pipewire-pulse wireplumber

sudo systemctl restart bluetooth

TLDR

I wondered for two weeks why the method described in the official Arch Linux guide, using the WirePlumber configuration file at /etc/wireplumber/bluetooth.lua.d/51-bluez-config.lua and syntax like bluez_monitor.properties = { It doesnt'work

Instead, use /etc/wireplumber/wireplumber.conf.d/50-bluez.conf and syntax described in the beggining of post and will be fine