I have an nVidia GeForce GTX 1080 with two daisy chained (MST) Dell U2715H monitors under Ubuntu 16.04.
The hardware and the OS has the DisplayPort 1.2 support and the drivers work properly.
I turned on DisplayPort 1.2 for both monitors and they show up in the settings and in the nVidia control panel, I can even move my mouse to the second screen (so the desktop is extended too). The monitor plugged to the PC works perfectly fine, but the daisy chained monitor (the one plugged into the other monitor) is somewhy stays in sleep mode so I have a black screen. Why? How can I fix this?