I think stuff might work for a while when screen is off but if the phone lies idle for hours, apps get killed etc. and the phone checks for notifs only once in a long while.

Pretty much, and I say this as an Android user. The OEMs brag about "long battery life!" but they're fucking up by hibernating apps in the background.

Until recently, one thing I hated in smartphones was task management. There was no way to kill an app and keep it dead, no way to manage what processes are running on the phone at any given moment. There were third-party task managers that sorta, kinda sometimes worked, but the phone fought you hard.

I'm kind of sympathetic to the phone vendors here - the app ecosystem is a mess, every app vendor feels way too entitled to their users' resources.

https://support.signal.org/hc/en-us/articles/360007318711-Tr...