Very similar for me with Acer V 15 Nitro with NVIDIA GTX 960M. When a display is plugged via HDMI black screen is present. When the GPU is set in prime settings (nvidia-settings) to Intel, everything works. Lightdm didn't help.
Ubuntu 16.04 LTS, driver 367.27, Ubuntu 4.4.0-28.47-generic 4.4.13
Very similar for me with Acer V 15 Nitro with NVIDIA GTX 960M. When a display is plugged via HDMI black screen is present. When the GPU is set in prime settings (nvidia-settings) to Intel, everything works. Lightdm didn't help.
Ubuntu 16.04 LTS, driver 367.27, Ubuntu 4.4.0-28.47-generic 4.4.13