Comment by Aachen

I'd be happy to check for you, but will need concrete steps. Signal working reliably is pretty much all I can confirm, since I don't use any others apps on that device that would give me notifications. Signal afaik uses this Google Cloud Messaging thing or whatever their TCP connection marketed as push service is called. Maybe that's now called Firebase?

But Signal can also fall back to websockets, which I use on my personal phone and that's working great without any battery loss so I don't know how to tell the difference