Recently I bought a new smartphone, yay. Being the privacy concerned individual I am, the first thing was to disable the location services altogether.
Great, I was happy, the new phone worked well for a day or two, then problems started.
First I expreienced delays in push notifications, later the notifications arrived only if the app was explicitly started.
This state was obviously a no-go, so I started investigating.
Checked the settings, all of them, tweaked the battery optimizations, not to disable my IM apps, but to no avail. The problem persists.
Asked Google, no usable answer…
Then it clicked: When I reviewed one of the cloud sotrage apps it asked for permission to use the device location for the sake of automatic picture upload.
With re-enabled location services the notifications are working as expected. Looks like one must waive some privacy to have a working smartphone.