Attempting to connect a second monitor through displayport renders Ubuntu 18 unusable

[markell]

I have Lenovo ThinkPad W510 running Ubuntu 18. When I connect my TV through the displayport the system becomes unresponsive - I can move the mouse, but there is no response. The TV screen shows No Video.
If I then disconnect the cable the laptop screen goes black and the only way out is reboot.

This laptop used to run Windows 10 before and displayport worked fine. Then it was Linux Mint and there the displayport also worked. So, I am pretty confident the hardware works.

I am at loss how to troubleshoot it.

The question is also posted here - https://askubuntu.com/questions/1104...-ubuntu-18-unu
But the view count is very low and there are no responses.

[Autodave]

Are there or did you install any driver for the Nvidia card? If so, what one and where did you get it from?

If you have not installed any, go to Settings -> Additional drivers and install the recommended one.