I download the apk file from Whatsapp website to install in GrapheneOS, and I've noticed that notifications for messages are very delayed from 15 minutes to no notifications at all until I turn on phone screen and then all of the messages come through. Is there other Whatsapp users with similar issues with functionality?
Signal functions good but there have been times of small delays with messages coming through to get a notification.
Hmm not exactly. WhatsApp is closed source, we don't know exactly how it works, but since it is based on XMPP, chances are high it uses xmpps own push service. Either there would be a notification about missing GCM or firebase.
Btw. Websockets on signal and telegram needs the apps running in background which eats up the battery. That's why a lot of degoogled-users install unifiedpush via ntfy-app. Some third party alternatives support unifiedpush, signal = molly + unifiedpush and telegram = mercurygram or nagram.