We use two Nextcloud for file sharing and backup, and recently tried out Nextcloud Talk for one-to-one video conferencing on our phones. It mostly works, but we do not have incoming call notifications.
After searching a bit, I found a forum post that linked to a feature request that explained a lot of what is going on.
Our LineageOS-based Android phones are completely Google-free. Push notifications in Google land are implemented via the proprietary Firebase Cloud Messaging that of course run on Google servers. Google gets information what phones register, what applications register, and when someone receives a push notification.
There is no alternative to that; applications either use google push services or they have to keep a notification connection open to their own server. (example) This drains battery when many applications are doing that, and so with each new Android version, Google makes it harder and harder to run persistent background processes.
OpenPush
F-Droid developer Marcus Hoffmann decided to do something and wants to implement a push notification system that can be used by any Android application, and the server component shall be self-hostable.
- Project homepage
- Project planning
- FOSDEM talk 2020-02 (slides)
- Client library
- Server implementation
I really hope this gets traction soon.