By using xrandr to force resolution settings (https://wiki.archlinux.org/index.php/Xrandr#Adding_undetected_resolutions ), I was able to obtain 4k resolution in the 4.8 kernel, but some flicker on the screen occurred, which was not there in the 4.4 kernel. Also that settings is temporary; logging out from the session brings me back to the full-HD login screen. So still some help needed here.
This message was posted on behalf of Intel Corporation
While Intel has not tested and validated Intel® NUC on your Linux version, we know that other customers have successfully installed it.
Intel suggests you check your Linux distro's website and forums at https://ubuntuforums.org/ with this graphics issue.
I would also recommend the Linux* for Intel® graphics support website
Thank you for your reply. I submitted a post in ubuntuforums.