I have not found any resources on setting up both the AMS and the external spool together on a H2S. I have the AMS PTFE tube fitted to the top orange port. The lower port has a rubber bung in it and no spring loaded locking collar.
Does this mean its not to be used?
Yes, sorry to say there is only one entrance, not two like the H2D.
Watch the unboxing video of the H2S; you’ll see that there’s only one filament input. Bambu Lab H2S | Large Format 3D Printer | Bambu Lab US Store
You need a splitter to be able to attach the external spool.
You can buy a 4-way splitter at Bambu or print any variant on Makerworld.
For the latter you will need extra PTFE tube inserts.