Currently, the Azure AD data provider only does the 'basic’ calls to the Graph API getting the fields from Azure AD (Entra) that are in the standard result set.
In some cases you want to get additional fields from for instance the user table like: Department, CompanyName, OnPremiseSamAccountName etc. This is achievable using the $select parameter in the API:

Unfortunately, the Azure AD data provider does not support customizing the request through RSD files.
It would would be very helpful when we are able to customize the calls through RSD files so we can access to all data from Azure AD instead of having to resort to a normal REST data provider to get this information.