Push Notifications Across Many React Native Apps without Firebase

My company creates white-labeled mobile apps using React Native & we need to setup mobile push notifications for each of those white-labeled mobile apps. What’s the right approach here?

Firebase & FCM obviously come out as a top search result, but the issue is that a new Firebase project would need to be created for each mobile app, which doesn’t seem to make sense given that there seems to be a limit on Firebase projects.

Note that we are operating at the scale of thousands of React Native apps (iOS and Android). Pretty much all research points to FCM, but that doesn’t seem like it’s scalable since each FCM setup process requires an explicit bundle ID, which is different for each app, requiring us to potentially have thousands of Firebase projects, which doesn’t make any sense.

We also looked into managed services like AWS SNS, but they just seem to require FCM to be setup in order to use their APIs.

Any guidance here would be helpful.