I recently upgraded from an iPhone 6 to a Samsung S10. I've always been able to play Spotify music from my iPhone to my aftermarket car stereo (Alpine CDA-117) via a USB cord. When my wife wanted to play music from her older S8, we swapped out the cord (to a micro USB) and it worked just fine.
The issue came up when I upgraded to my new S10. When I connect this phone, instead of playing the music from Spotify, it reverts to playing ringtones and notification sounds from the phone, as if they were on a playlist. I can't seem to get the phone to "send" music via Spotify through the USB-C cord, as the stereo only seems to recognize the system sounds. Spotify doesn't recognize the device, and it doesn't change anything if I already have the music playing before connecting. It simply plays music out of the phone as if it were not connected, and the car stereo simultaneously plays the system sounds.
Is there a way on the Android platform to designate which app or which audio source is permitted to transmit data via USB?