Check this radio app (APK) on your (test) devices:
We have discussed the problem with audio streaming intensively also in the AI2 (power user) forum among the power users and the App Inventor team. There currently doesn’t seem to be a solution for some devices (especially with Android 9).
(Unfortunately I can not refer to these threads because they are only visible to power users.)
@Ken Does my test APK work on your S8 (Android 9)?