Updated with 18.104.22.16801 Graphics Driver. Now HDMI works but still can't get 2650x1080 working. Tried to set a custom 2650x1080 at 30Hz but the monitor doesn't like it.
How to setup Custom Resolution for the LG Ultrawide?
Seems like it should detect the monitor and set it properly like every other graphics driver over Displayport (it even works on my Mac)
I am using same graphics controller and I was able to set custom resolution 2560*1080 at 30Hz with Display port and HDMI cable.
I tried with high-quality cables for both video ports. I did not use video adapters, just straight video cables.
Please try using different cables or try updating to the latest graphics drivers version:
Finally got back to this problem.
Uploaded all the latest drivers.
I can get HDMI to run at 2560x1440.
Using a DP->HDMI cable that handles 2560x1440 on the Mac Mini I cannot get the NUC to recognize and display 2560x1440. I'm OK for now since I only have one wide monitor.
Also noticed that sometime when just using a single HDMI monitor there's no display occasionally during startup and I need to hard reset and restart the NUC.