Azure.Identity recently changed from calling the deprecated:
AbstractAcquireTokenParameterBuilder<T>.WithAuthority(AuthorityHost.AbsoluteUri, tenantId);
to this:
UriBuilder uriBuilder = new UriBuilder(AuthorityHost)
{
    Path = tenantId
};
builder.WithTenantIdFromAuthority(uriBuilder.Uri);When adfs is passed as the tenantId, WithTenantIdFromAuthority throws because tenantId is null.
I looked at the MSAL code and this is the reason we end up with a null TenantId
This creates an AdfsAuthority which hard codes null as the TenantId
Ideally WithTenantIdFromAuthority should handle the ADFS case and do the same thing as WithAuthority(AuthorityHost.AbsoluteUri, tenantId) does.