Within the new ArcGIS Feature Service reader (part of the Esri ArcGIS Connector Package) if you choose a source type of Enterprise it’s not possible to connect to a feature service that is shared across an entire organisation and not in a group.
This can be done if you use a Source Type of Standalone Server (but it’s not obvious).
It would be nice to have and Item Source of Organisation which would allow connection without specifying a Group
