Hide "Sign up" Button in SSO case

Hi all,

just wanted to ask, if you could have the “allow new registrations” setting enabled, but don´t show the “Sign up” button, because sso is on, and that creates the account with the data in the oauth token on the fly.
So anyone with an existing account and with no existing account just need the login button to enter the forum.

I could do it with css, but is there a “conventional” way to do it ?

Thanks and Greetings!