I am observing the same "killing" of background service for Signal app too. Basically any app with a long-running session which you don't whitelist. And it seems that it whitelist the Spotify for example on its own. I don't think the blocking install by VLC team is the right way, communicating the issue to a user is a much more reasonable way. Look at Garmin Connect app, which had the same issue but they implemented notification and how-to disable management.
That is normal. An application that requires the background "foreground" service to run is obligated to display a notification and call an Android foreground service API in the service itself. Unless it is lower target SDK than 23 (number may be wrong).
