I have been using Samsung flow for a while with my Galaxy Note 9 and a Windows 10 laptop (Samsung brand).
When connected to Samsung Flow through Wi-Fi LAN and enabling the Smart View feature, the two ways that I can think of in order to hear the audio output of my Galaxy Note 9 are:
One partially working way that I found is:
Settings > Sounds and vibration > Advanced sound settings > Separate app sound
This feature allows me to route a single app's audio to a Bluetooth device, so in this case I can hear the audio when connected to Samsung Flow; however, it is limited to only one app. So when playing background music and a game simultaneously while connected to Samsung Flow, hearing the audio of both the music app and the game is not possible.
Has anyone had luck properly hearing the phone's audio over Bluetooth, when connected to Samsung Flow?
It should have a it's own setting to keep sound routing through the phone.
Excellent work around that you found. I'm now using it until Samsung updates the app to give us a setting for it.