Actually, because of the design of the DP-to-HDMI IC used in this design, the HDMI firmware is completely separate from the BIOS and other firmware.
In order to install the updated firmware, you need a HDMI 2.0-compliant monitor/TV properly connected using a HDMI 2.0-compliant cable.
Apologies but I was not talking about the HDMI firmware - I was talking about the BIOS of the NUC itself.
I keep seeing the requirement for an HDMI 2.0 device when updating the BIOS. Cannot figure out why that would be necessary to update a system BIOS.
That's what I am saying. It is NOT required to install BIOS Updates. It IS required to install HDMI firmware updates, however. Anything you read to the contrary is just plain wrong.