Automatic sso login
According to OAuth2.0 standards, at the time of authorizing this is not possible to tell SSO provider like Google in advance which user account is going to be used. But still needs to check particularly with OAuth2 implementation of Google. 
According to standards, user credentials like user name and password should only be challenged on SSO providers(IDP's) page.
I want to implement sso for multiple providers in my app.
Currently I am using flask-oauthlib for the authentication. For google authentication sso login works like a charm. 
Since I will have multiple sso providers, I was wondering if I could simply have one text field on my landing page, and then redirect the user according to the email domain to the right sso provider while automatically initializing the handshake process. 
The question is, to whether I can automatize the sso login, without having the user to select their account on Google's Choose an account page; thus saving an additional step?
I hope this makes sense, thank you!