Did you try turning battery optimization off though? It can be quite agressive. In my experience it never stopped background music players so it might really be something else, but background sync of non-system apps does not work reliably for me with enabled battery optimization.
No, that would definitely cause issues like that. It’s why at very least FairEmail explicitly asks to be excluded from battery optimisations.
I never use external speakers so I can’t confirm the Spotify issue but WhatsApp works fine in the background for me as long as it is started once after starting the phone so it can start that WhatsApp background notification.
Well shit, thank you all for such fast replies! And of course, it seems that you’re completely right. I’ve disabled battery optimization for the affected apps and it looks like that solved the problem! I’m surprised that it’s so aggressive, but there you go.
I’m sorry for not investigating further before bothering the community here; and thanks a lot for helping me out anyways! It’s much appreciated