In documentation for Auth with Facebook says:
Make sure your OAuth redirect URI (e.g. my-app-12345.firebaseapp.com/__/auth/handler) is listed as one of your OAuth redirect URIs in your Facebook app's settings page on the Facebook for Developers site in the Product Settings > Facebook Login config..
But when I try it with my link - it not redirect at all (https://someproject-8fda3.firebaseapp.com/__/auth/handler). In console Auth with FB is switched on. But I still don't understand why it's not working (with google auth - same problem).