I noticed that so many web apps use Firebase as their backend service. I found firebase2graphql, a CLI tool to help you try realtime GraphQL on your firebase data. It takes data exported from firebase and imports it into Postgres via Hasura GraphQL engine.
I had to build an app from scratch for this, it really helped cement a lot of GraphQL operations because you have to configure the app to display data the GraphQL way when changing from Firebase. Have a look at the video
Let me know if this was useful for you and if you'd be looking to migrate.