Can Excel PowerQuery authenticate using IdentityServer4?

Question

I've been trying to migrate an application from using an AAD instance to using an IdentityServer4 instance. I had the application working with PowerQuery for Excel when I was using AAD. I did this by responding with a 401 response and a header "WWW-Authenticate: Bearer authorization_uri=MyAADuri".

Now moving this URI to IdentityServer4 my attempts to login with Organizational Account returns "The token service reported by the resource is not trusted".

Reading here (https://learn.microsoft.com/en-us/deployoffice/security/identity-authentication-and-authorization-in-office) it appears that the Organizational Accounts must be provided by MS providers like AAD or Office 365. Is there any way to work around this to allow us to use our own IdentityServer4 implementation?

Answer 1

We have received a response from MS support. It is not possible to use PowerQuery or Power BI (same connector) with IdentityServer4, or for that matter any other custom token provider. Only Azure AD will work, and there is no way to make it trust any other token provider.