The official Bluesky app uses Firebase Cloud Messaging (FCM) for its push notifications, and I think runs some kind of backend on their own server? samuel.fm said that there's a reimplementation in the graysky repo that's quite simple!
Bluesky app fork with some witchin' additions ๐ซ
witchsky.app
bluesky
fork
Kind of looking into this, just wanted to flag what i think is the graysky implementation?
https://github.com/mozzius/graysky/blob/main/apps/expo/src/lib/hooks/notifications.ts