You should have been through the setup of the Firebase Core before attempting to proceed with Remote Config.
Make sure you have added all the extensions required for the Firebase Core extension as outlined here.
The only required additional ANE is the Remote Config ANE located in this repository:
This ANE contains all the required libraries for the main Firebase Remote Config functionality.
The following should be added to your
extensions node in your application descriptor to identify all the required ANEs in your application:
ComponentDiscoveryService service you added as part of the core Firebase manfiest additions and add the following meta data tags:
It should now appear like: