PeterWaldron, Thank you for posting in the Intel® Communities Support.
Just to let you know, the Intel® NUC Kit DN2820FYKH is under status of: End Of Interactive Support / Discontinued, as you can confirm in the following link:
As an option you may want to try our Discontinued Products Community to get recommendations from fellow community members.:
Or you may also find the Discontinued Products Website helpful to address your request:
Intel Customer Support Technician
A Contingent Worker at Intel
That's the correct BIOS identifier and even the correct version. Just in case, I have attached a ZIP file containing the .BIO file and the release notes.
Place this .BIO file onto a USB flash drive, insert the drive into the NUC and then press F7 during the boot process. You should set a dialog that allows you to select this USB flash drive and then this BIO file. The BIOS upgrade should progress on its own from there, providing a display of its progress onscreen.
Hope this helps,