AAD Application Proxy and B2B Users

Hi, I assume you are looking to use the app proxy for organizations with on-premises apps which are using Windows authentication.  We are currently working on the documentation for this scenario which should be posted to docs.microsoft.com shortly.   In principle, creating an account in a AD domain corresponding to a user in Azure AD, including a guest user, would enable the app proxy to match the user coming in from Azure AD and use KCD for impersonation and permit that user to then access Windows integrated authentication, however there are a number of account lifecycle subtleties here.  So even if you see the app proxy is able to permit the communication flow, I'd suggest waiting for the documentation as there are a number of deloyment considerations and best practices to look at (e.g., what container to put the users in, when to deprovision the user from AD, how to avoid RID exhaustion and end user confusion about "All authenticated users" etc)  Feel free to reach out to us if you have additional questions.  Thanks, Mark