Use external IDP as SAML authentication contract

Hi all!

I'd like to know if there is a way, that doesn't involves the developement of a custom class, to trigger a SAML authentication to an external IDP for an SP configured in the Identity Server? I understand that a possibility to do this is with a custom class that triggers an spsend authentication, but i'm exploring if there is an out-of-the-box way.

Thanks in advance!