Did you already try booting with the 9980xe on the HJ5Y7 board, with most recent bios, and got a black screen?

I know it's officially unsupported, and that word on these forums is a bios update would not be released, and the bios block is consistent with how Dell has been treating other systems lately.  I only ask because one user back in April 2020 or so said the update was added (and not mentioned) to a recent r4 bios update.  His statement was never confirmed by any other user though so no idea if its correct.  His username was something like redxps if that helps.

For sake of clarification, 

The system in questions is an Area 51 R4

I found the post here:  https://www.dell.com/community/Alienware-Desktops/Area-51-R4-vs-R5-Dell-did-a-nice-thing-to-users/td-p/7538451

@Raven1366  But yeah, area 51 should have been clear when you mentioned 9980xe. 

I have tried and get a black screen. The motherboard doesn't beep though.

I will try to find the post you are referring to. 

Will update further if anything changes.

@r72019 , thanks for the help mate.

The amendment was per request of moderators.