You are looking to enable Heroku Single Sign-on (Heroku SSO), and want to make sure your identity provider (IdP) is supported.
Heroku supports SAML 2.0. Most identity providers (IdP) support SAML 2.0. Our list of verified IdPs can be found here: https://devcenter.heroku.com/articles/using-sso-services-with-heroku#built-in-sso-support-for-heroku-from-major-identity-providers-idps.
To configure Heroku SSO with a different identity provider, please follow the directions here: