Just trapped into the same issue, described in https://community.roonlabs.com/t/roon-rock-uefi-intel-nuc-not-showing-hdmi-output.
Since I want to add Windows 10 an a separate SATA drive which needs UEFI boot, I thought it wouldn’t be a bad idea to reinstall ROCK with UEFI using current USB image 254. And then, being able to get a simple boot selection between ROCK and Windows.
My NUC8 is able to use legacy and UEFI boot.
The updated installation instructions for ROCK state that, in case it’s necessary, ROCK would be updated to the latest version (256) automatically. This didn’t happen with my NUC8, though ROCK is installed and running with UEFI, and legacy boot is disabled.
That said, I had the same issue with audio over HDMI since no HDMI ports are shown in roon client. The only accessible port shown was the analogue audio port.
Then, I followed the manual steps also explained in https://community.roonlabs.com/t/roon-rock-uefi-intel-nuc-not-showing-hdmi-output. They worked. HDMI ports are now all visible and working (select HDMI 0).
@roon: Please update your install/update steps for ROCK. Maybe your current ROCK update check only looks for the used NUC model and not for the actual boot condition (legacy/UEFI) under which ROCK is running?
Thanks!