I use MSAL.js to authenticate to Azure AD. For some users with email addresses matching a specific domain name, Azure AD redirects them to a third-party Identity Provider (IDP) where they can authenticate before being redirected to my application.
It appears that from time to time the third-party IDP is not responding (known issue that affects all applications of my client apparently). Is it possible in this case to fallback to Azure AD as the IDP ?
In other words, is it possible to have multiple IDPs for a single User Principal ?
For an external user object in Azure AD there can be only one external IdP. Currently there is no fallback mechanism for the scenario you are looking for.