Comment by Zak
15 hours ago
It's theoretically possible to just keep an app running in the background all the time and periodically poll a server.
That's unreliable though since some OEM Android builds will kill it for that even if the user disables battery optimizations. Those OEMs sort of have a point; if lots of apps did that it would drain the battery fast.
Then that's basically what I said right? That there is in practice no way to opt out of using Firebase if you want consistent notifications.
Not clear what your point is. The Signal server wakes up the app via an empty message. At most the info this conveys is that a Signal app got a message to pull.
My point is there is no reasonable way to remove oneself from Google and Apple even with a fully custom application, they control the notification servers for their devices.