@mgetka thanks so much for the explanation.

"to redirect iOS users directly to pseudo protocol. And redirect all the android user to a custom interstitial site. "
I believe this would be the only option for the time being.

Deep Linking doesn't work at least for my application:
Flutter -> flutter_appauth(4.0.1) -> fusionauth

While the same scenario could work with Auth0, following this blog.

Comparing with the solution with FusionAuth.
FusionAuth open a new tab for Facebook and Google login.

While Auth0 continues on the same page with a page redirection.