Screen off Option?

[bitmap]

Depends on your platform. Android app has an audio-only option that may work with the screen off (though it says "in the background") but might be designed to function only when browsing other apps. Will test in a sec and edit with results.

   

EDIT: Can confirm, works with the screen off. Requires the built-in player, the option shown enabled, and when you leave the app, drag the PiP window to the X that appears to dismiss it (I think clicking the X in the PiP window kills playback). Or you could leave the PiP bubble, as it probably doesn't matter.