NVIDIA + Ubuntu blank screen, but working with nouveau


I’ve spent a few days looking into a blank screen issue I have with using the nvidia-driver-390 on Ubuntu, and would really love some help.

Attempting to use an external 34" display (3840 x 2160, LG 34WL500) results in a blank screen when using the nvidia drivers (I also tried 418). I have also tried reducing the resolution, but no joy. The laptop fails to even recognise a external display is plugged in when using the nvidia driver in on-demand or intel prime mode.

However… when using nouveau I am able to display at 2560x1080 on the external display. I suspect the issue could be the laptop (Macbook Pro Retina 15" early '13 with GeForce GT 650M) is just not capable.

What I would like to know is:

a) am I even able to use the dedicated GPU for the external display?

or if not

b) is it possible for me to have the nvidia driver installed but use the integrated (Intel) for the external display, and run in on-demand mode so at least the dedicated GPU can be used for some processing?

Any help would be much appreciated! Thank you.

nvidia-bug-report.log.gz (192.4 KB)