Use companion app as media player

I want to use a old mobile phone to stream radio station. With Radio Browser I can get the stations I want. When adding the Media control card to my dashboard I need to select an Entity. In my case there are only 2 entities listed, but both I the mobile phone. How can I add the mobile phone to the list of entities?

Thanks, Corné

I am also looking for a solution to this. Recently tried to get music assistant installed and I don’t have any way to play it to my phone. Was totally looking for a way to get a morning workout playlist going when I turned on my Bluetooth headset in the morning (ideally without Spotify). So far it looks like we need some kind of castability on our phones or some way for it to act like a receiver for casting.