Will not play YouTube via Bluetooth or UBS in a 2012 Toyota Highlander any suggestion.

I have no idea why you want to play just audio on Youtube, but it's not desiged to be an audio source for other devices through BT or USB. To play the audio, connect from the headphone jack to an auxilliary input to your car stereo.

It's not supposed to play "YouTube via Bluetooth or UBS (sic)".

Neither Bluetooth or USB carry video for any device.

I don't know that the audio would be sent out via the Bluetooth for a video off Safari or the You Tube app.

The You Tube app probably does not access the audio out for Bluetooth.

As I said, the Youtube app is not designed for that. Contact Google, who develped it.