@Umeey_US for push notifications, it depends on what you plan to use to actually dispatch notifications to Apple and Google so they are pushed to your users’ devices.
In our case, we needed our system to integrate with Expo’s Push Notification service, so we ended up building our own plugin for this.
However, if you wanted to use something like OneSignal, you could leverage the existing work done in the Discourse OneSignal plugin.
Perhaps there are other plugins that integrate with similar services that you could use.