Flipping the wifi/bt killswitch is sufficient. Here's a short video. The audio quality isn't great but you can hear the switch from speaker to the car's audio:
The cover art needs work on the bluetooth side as we don't send that yet but apart from that it works nicely (skipping songs forwards, backwards, etc).
@devrtz@thomzane@agx Calls require HFP/HSP profile instead of A2DP. While BlueZ and PipeWire/PulseAudio can do it, most phones need work on the ALSA UCM side and also drivers for their Bluetooth chip and audio.
@agx Do calls work through the car?