After upgrading to LineageOS 17.1 I wasn’t able to play any audio via bluetooth connection from my Xiaomi Mi 8.
To fix this issue, just go to developer options and disable Bluetooth-AD2P-Hardware-Offload and reboot your phone.
If you notice “error: a2dp-source profile connect failed for protocol not available“, probably in the log or via systemctl
sudo cat /var/log/syslog | grep -i protocol
#or
sudo systemctl status bluetooth
open the bluealsa.service file
sudo nano /lib/systemd/system/bluealsa.service
and append the a2dp-sink:
ExecStart=/usr/bin/bluealsa --profile=a2dp-sink
Now reboot. Check with
sudo bluetoothctl show