if you just want audio & your car doesnt support Bluetooth you could use an adapter to take it from Bluetooth to 3.5 aux. if your car is so fancy it doesn’t have aux input you can get a Bluetooth to FM radio adapter that will take over one the channels in your car as well.
outside of sandboxing/limiting android auto via grapheneos good luck.
if you just want audio & your car doesnt support Bluetooth you could use an adapter to take it from Bluetooth to 3.5 aux. if your car is so fancy it doesn’t have aux input you can get a Bluetooth to FM radio adapter that will take over one the channels in your car as well.