Secondary display stopped working

Asked by Hugh O'Neill

Ubuntu 20.04 on dual boot Win 10 Dell Inspiron 15 3000 using Acer G276HL as additional screen via HDMI.

Use of the additional screen has ceased and the 'Display Settings' utility does not now 'Apply' this screen either as 'Join' or as 'Mirror'. The setting automatically reverts to 'Single Display'.

When booted to Win 10, the additional screen functions as expected. I have made no changes to any settings at all.

Is there a fault in this Display Settings utility? Was it changed in a recent update? How can I get back to using my additional screen, please?

To help, the xandr listing is:

hugh@hugh-Inspiron-3501:~$ xrandr -q Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 16384 x 16384 eDP-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 344mm x 194mm 1920x1080 60.00*+ 59.97 59.96 59.93 48.00
1680x1050 59.95 59.88
1600x1024 60.17
1400x1050 59.98
1600x900 59.99 59.94 59.95 59.82
1280x1024 60.02
1440x900 59.89
1400x900 59.96 59.88
1280x960 60.00
1440x810 60.00 59.97
1368x768 59.88 59.85
1360x768 59.80 59.96
1280x800 59.99 59.97 59.81 59.91
1152x864 60.00
1280x720 60.00 59.99 59.86 59.74
1024x768 60.04 60.00
960x720 60.00
928x696 60.05
896x672 60.01
1024x576 59.95 59.96 59.90 59.82
960x600 59.93 60.00
960x540 59.96 59.99 59.63 59.82
800x600 60.00 60.32 56.25
840x525 60.01 59.88
864x486 59.92 59.57
800x512 60.17
700x525 59.98
800x450 59.95 59.82
640x512 60.02
720x450 59.89
700x450 59.96 59.88
640x480 60.00 59.94
720x405 59.51 58.99
684x384 59.88 59.85
680x384 59.80 59.96
640x400 59.88 59.98
576x432 60.06
640x360 59.86 59.83 59.84 59.32
512x384 60.00
512x288 60.00 59.92
480x270 59.63 59.82
400x300 60.32 56.34
432x243 59.92 59.57
320x240 60.05
360x202 59.51 59.13
320x180 59.84 59.32
HDMI-1 connected (normal left inverted right x axis y axis) 1920x1080 60.00 + 50.00 59.94
1920x1080i 60.00 50.00 59.94
1680x1050 59.88
1280x1024 75.02 60.02
1440x900 59.90
1280x960 60.00
1280x800 59.91
1152x864 75.00
1280x720 60.00 50.00 59.94
1024x768 75.03 70.07 60.00
832x624 74.55
800x600 72.19 75.00 60.32 56.25
720x576 50.00
720x576i 50.00
720x480 60.00 59.94
720x480i 60.00 59.94
640x480 75.00 72.81 66.67 60.00 59.94
720x400 70.08

As you can see, the HDMI screen is not shown as being active but it used to work under both Ubuntu and Win 10 on this same dual boot laptop but now it only works under Win 10.

What can I do to get this additional display to work again with Ubuntu?

I just found this and tried it to no effect:

https://itectec.com/ubuntu/ubuntu-second-monitor-suddenly-cant-be-detected-ubuntu-20-04-1-lts/

Getting desperate now - I need my secondary screen to work!

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Revision history for this message
Hugh O'Neill (squarelevel) said :
#1

Just occasionally, during Ubuntu startup, the Dock appears on the left of the otherwise black secondary display. Does this give anyone any clue to what's happening and how to fix the above?

Revision history for this message
Bernard Stafford (bernard010) said :
#2
Revision history for this message
Hugh O'Neill (squarelevel) said :
#3

Thank you very much for responding, I really appreciate that.

However(!), the problem exhibits itself in the 'Screen Display' settings, in that after choosing 'Join Displays' and immediately after clicking 'Apply', the setting immediately reverts back to 'Single Display', with only the 'Keep Changes' and 'Revert Setting' options available. So the changes have not been retained, nor do I wish to 'Revert' because it already has!

There would definitely seem to be something faulty about this in the Ubuntu environment, because when booted to Win 10 the dual displays work as expected.

I am really stuck here. Do you have any more ideas please?

Revision history for this message
Hugh O'Neill (squarelevel) said :
#4

Just for the hell of it, I ran clamscan. Although no infections were reported, the dual screen option now works - but - I cannot get the secondary screen above the primary. Moving them in the gui doesn't retain those positions and only puts them side by side. I had this problem originally and solved it with a command line but I've lost that record and don't know how to recreate the command. I've also tried using ARandR but the vertical positioning instruction is not obeyed. Or should I post a new query, as my basic one appears to be fixed by having run clamscan?

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