Disclaimer: This question is only relevant for the use of the audio-service plugin (version 0.18.1 or higher).
What would be the best way to receive background updates regarding song titles? Imagine I listen to a radio station (via an mp3 stream) and receive song updates via a websocket connection. Where should this websocket connection be made? In the AudioHandler? Or in an entirely new isolate?
As the main (UI) isolate can be killed/halted when in background use, the app should still receive information about song updates in the background and display them in the control center etc.
As the main (UI) isolate can be killed/halted when in background use,
You have a misunderstanding here, audio_service is specifically designed to keep this isolate alive when in background use. The only reasons I can think of for the main isolate to be killed when it's in background use is if the OS is running out of memory (in which case any other isolate you start will also be at the same risk), or if you didn't set up your main activity on Android as per the instructions to use the FlutterEngine that audio_service keeps alive. But in the normal case, you should not have run into this problem.