So dual 4k monitor set up works flawlessly on Windows 10. Connecting two DP to a MST or one DP and HDMI. Either combination works perfectly. However on Ubuntu 16.04 with combination of kernel 4.7.x/4.8.x/4.9.2, and NVIDIA-367/375 Ubuntu will crash with the MST. With kernel 4.4.x it will not crash. However one 4k will work via HDMI but I have to turn off the laptop screen. I know if I connect two monitors with a resolution lower than 3840 × 2160 works fine on Ubuntu. I've connected 2 3k monitors and they work on Ubuntu but at work I have 2 4k monitors and my RB is my work computer. Has anyone successfully connected a 4k monitor via USB-C? If so which kernel and driver are you using? What is the model of the monitor? Any help would be greatly appreciated!