[Slawek]

Is it possible to have phone media audio play through my car speakers when the source is FM radio? I am using an Android phone and it is typically plugged in by a USB cable as I always have Waze up and running. When I launch Google Assistant to do voice commands there is no feedback because the phone is connected to Bluetooth and I'm listening to the FM radio.

When I had an iPhone this would not be a problem because Siri would be activated as a phone call so it would always take precedence. If I want to stream Spotify, that is a different story and I know I have to switch the source to Bluetooth.

This becomes an issue when I have my phone connected with Bluetooth and I want voice commands using my phone but I am listening to the FM radio source.

 

[Fif]

There are some Xposed modules that can do what you describe.
For example: repo.xposed.info/module/com.gomez.btscoaudio

However that involves hacking your phone to the same extent as your car. That's definitely not for the faint of heart.