There's no Facebook SDK yet on Asset Library, so you're on your own. Facebook integration is just like standard REST API (all of the SDKs are just wrappers around), so you can use the HTTPClient object to make API calls.
The process for publishing to Facebook is similar in both engines - you will need to register as a Facebook developer, integrate the Instant Games SDK, and submit your game for review.
There's Google Play SDK on Asset Library, but I'm not sure if it's updated for the latest Godot Engine.