Push notifications are such a great way to spy on people, because so many apps send highly private information as push notification. Even if you install them on-premise, because the only well-supported battery-friendly way to send notifications is through Google's and Apple's servers.
The most serious of secure messengers moved to push notifications that just cause the app to wake up and fetch the real message from the server to show as notification, but there are still plenty of apps that just send the full message as push notification.
The most serious of secure messengers moved to push notifications that just cause the app to wake up and fetch the real message from the server to show as notification, but there are still plenty of apps that just send the full message as push notification.