Thanks for the reply.
The link below states that "This system was tested with 16.04 LTS, running the 4.13.0-1008-oem kernel".
So I am pretty sure that the generic ubuntu kernel did not have the supported drivers and someone at Dell too had to somehow re-compile the drivers and make it work with the Ubuntu 16.04 image that shipped with the machine.
If I could get ready-compiled drivers it would be awesome! If not then I would be happy to get the driver source, compile it myself and install it, if Dell could let me know the steps on how to do it.
Thanks & Regards,