We're using the ITfoxtec Identity SAML 2.0 library version 4.8.8 with a .Net Core product, have implemented SSO successfully with Azure AD as the idP, and would like to avoid the "Pick an account" dialog. We have a custom login page that asks for the identity's email address and want to supply that value as the only valid identity to authenticate with.
We cannot use the Subject property of a Saml2AuthnRequest because AAD doesn't support it (https://learn.microsoft.com/en-us/entra/identity-platform/single-sign-on-saml-protocol#authnrequest), and cannot find how to supply a login_hint. Any help is appreciated.
As of my knowledge Azure AD only support login_hint in OpenID Connect and do not support anything similar in SAML 2.0.
Similar functionality in SAML 2.0 is to add an NameID with the email format in the subject element. The functionality is supported by FoxIDs but not supported by Azure AD.