Android app architecture: JSON file + Firebase -> local database?

I'm developing an app whose main data is stored in a big Json file. However there are some additional information, provided by logged-in users, that are retrieved from Firebase Firestore. What's the best app architecture for this scenario? a) keeping the Json file and using Firestore as a layer on top of it, updating the information in the UI with the data donwloaded from Firestore? b) saving the Json file in a local database (updated with data coming from Firestore) which should act the "single source of truth"?

What do you think?