I have questions (see picture)

What is it for?
Looks like it could basically be a PCIe x8 equivalent.

I googled that model of Dell and the CPU replacement didn’t have that little end on it

When I search that specific model on eBay, they all seem to have it.
my first guess would be additional CPU-to-CPU interconnects without sacrificing anything else and not needing a new socket or board… probably just something in UEFI, maybe.

I think the little tab thingy was for intel omni connect or something, although thing it was only for a super small set of boards/users. as the Knights Landing CPUs are normal LGA3647 afaik.