The Firebase SDK has exposed a withConverter() method, on a Document/CollectionReference and Query, since 7.6.0 (https://firebase.google.com/support/release-notes/js#cloud-firestore_15)

It would be great to see that exposed in react-native-firebase.

API Reference here:

https://firebase.google.com/docs/reference/js/firebase.firestore.FirestoreDataConverter