I was actually refering to an earlier post about no HD Audio pass-through, not your issue.
When you replied I was thinking you had the audio issue. Apologies.
For those needing the HDMI firmware fix on NUC8 its called:
NUC8ixBE-HDMI-FW-Update-Version 1.78.4.0.4 and has a Windows only exe method to push the firmware to the NUCs HDMI.
For my LE NUCs I created a bootable Windows 10 USB key and ran the firmware exe on that (it has a UI and won't run on DOS). After rebooting back to LE my Atmos/TrueHD passthrough now works perectly.
I have the zip I downloaded but no link on MS or Asus now Asus has take over NUC support.