It is possible to create a portal which allows an Azure AD login as well as sign up / sign in with a separate entity such as Azure B2C, which is used by external customers. Ideally, it would be useful to allow separate pages for logging in, one for B2C/external and another for Azure AD or SSO for internal staff.

This would be beneficial to the end user from a user journey perspective as well as a security perspective as an external user could attempt to compromise a staff login option.