displayport on Ubuntu 22.04 with Nvidia GTX 1070

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I put Kubuntu 22.04 on an Alienware laptop with Nvidia GTX 1070. It installed the drivers etc for Nvidia, version 525 (with the ubuntu-drivers command).

I have two external screens, one connected with HDMI and one with DisplayPort. The screens are identical, the one connected with HDMI works fine, the one with DisplayPort switches off. When I swap them round, again the DisplayPort connection is the one that switches off.

Switching cables etc gives the same result. No luck with DisplayPort. Apart from the card being faulty, which I don't think it is, it seems reasonable to think Ubuntu 22 is the problem.

There are many posts about DisplayPort and Ubuntu 22, but no definite solution? Is it necessary to downgrade the driver, or to wait for an upgrade that fixes this?

Some diagnostics:

The output of xrandr is:

Screen 0: minimum 8 x 8, current 3600 x 1080, maximum 32767 x 32767
HDMI-0 connected 1680x1050+1920+0 (normal left inverted right x axis y axis) 474mm x 296mm
   1680x1050     59.95*+
   1280x1024     75.02    60.02  
   1152x864      75.00  
   1024x768      75.03    60.00  
   800x600       75.00    60.32  
   640x480       75.00    59.94  
DP-0 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 194mm
   1920x1080     60.02 +  47.99* 

and 7 more HDMI/DP numbers that all say "disconnected".

In the "Nvidia X server settings" interface, there are 2 lines under "GPU 0" (which is the 1070):
--HDMI-0 (the working screen)
--DP-0 (the DisplayPort)
and then under DP-0 it says:
-Chip location: Internal
-Signal: DisplayPort
-Connection link: 1 lane @ 2.70 Gbps
-Refresh rate: 47.99 Hz
-DisplayPort connector type: DisplayPort
-DisplayPort multistream available: No
-DisplayPort audio available: No
-G-SYNC mode available: G-SYNC
-G-SYNC mode available: G-SYNC

Does that mean that DP-0 is detected, but cannot be used?

I sit in a Tesla and translated this thread with Ai:


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