How to check that? I searched the BIOS but couldn't find any FW number. Also i installed Libreelec from scratch and the same result:
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767
DP1 disconnected primary (normal left inverted right x axis y axis)
DP2 disconnected (normal left inverted right x axis y axis)
DP3 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
1920x1080     60.00 + 120.00   100.00   119.88    50.00*   59.94    30.00    25.00    24.00    29.97    23.98
4096x2160     24.00    23.98
3840x2160     30.00    25.00    24.00    29.97    23.98
1920x1080i    60.00    50.00    59.94
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
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)
So i'm missing the refresh rates above 30Hz on 4K.
Frans