I am trying out the new Firebase/Crashlytics setup and seem to run into a weird issue.
This takes me a lot of time than I figured out how to migrate correctly. Actually you have two ways how to do it:
Perform clean migration without keeping crash history from Fabric Crashlytics
This way is described in Firebase Crashlytics developer guide. You have to here remove com.crashlytics.ApiKey meta-data from app manifest file.
With this way you must not link Fabric with Firebase otherwise crashes will not shown in Firebase nor Fabric console.
Link Fabric with Firebase and keep the crash history
This way is probably nowhere documented. Crucial is here to keep com.crashlytics.ApiKey meta-data in your manifest. Then you need to link Fabric Crashlytics with Firebase. You can also enable forwarding Events (formerly Answers) to Firebase Analytics. Both actions are presented in Fabric console, look for Firebase in a side menu.
All new crash reports show up in both Fabric console and Firebase console. Also this linking arrange a copying all Fabric crash report history to Firebase.
I think firebase-core artifact is not necessary here, but I added it. I'm also using Fabric Events, so with firebase-core additional app usage events was appeared in Firebase Analytics.