[_Spook_]

Yes, until Kodi Dev or Intel Dev resolved the HDMI 2.0 issues, the only MINI PC (NUC Like) that has both HDMI 1.4 and 2.0 is the AsRock Beebox.

Asrock has integrated some adapter to convert DisplayPort to HDMI 2.0.

Code:

$ xrandr --display :0
Screen 0: minimum 8 x 8, current 3840 x 2160, maximum 32767 x 32767
DP1 disconnected (normal left inverted right x axis y axis)
DP2 connected 3840x2160+0+0 (normal left inverted right x axis y axis) 1600mm x 900mm
   3840x2160     60.00 +  30.00    25.00    24.00*   29.97    23.98  
   4096x2160     24.00    23.98  
   1920x1080     60.00    50.00    59.94    30.00    25.00    24.00    29.97    23.98  
   1920x1080i    60.00    50.00    59.94  
   1280x1024     60.02  
   1152x864      59.97  
   1280x720      60.00    50.00    59.94  
   1024x768      60.00  
   800x600       60.32  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       60.00    59.94  
   720x400       70.08  
HDMI1 disconnected (normal left inverted right x axis y axis)
HDMI2 disconnected (normal left inverted right x axis y axis)
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

Yes, they use a chip to convert DP to HDMI 2.0x. Intel does the same in the NUC6i7KYK (Skull Canyon) and now with the NUC7.

The intel and kernel devs need to implement the LSPCON patch into the i915 drivers to makes the use of proper HDMI 2.x possible since HDMI 2.0 on Kaby Lake is native. Not sure what the latest status for these patches are. But you can find more about the patches here:
https://patchwork.kernel.org/project/intel-gfx/list/

It's not a Kodi bug/problem.

EDIT: Seems the LSPCON patch work has been implemented into the 4.10 kernel chain. So time will tell https://bugs.freedesktop.org/show_bug.cgi?id=94248