Score:1

Unknown display in Ubuntu 20.04

in flag

I'm using Ubuntu 20.04 (Linux kernel 5.11.0-34-generic) on Dell XPS-15-7590 and I've found a weird thing. When I connect my laptop to an external monitor by HDMI first and then boot, only the external monitor can be used and the internal screen cannot be wakened. However, if I connect my laptop to the external monitor AFTER booting, the external monitor receives no signal and only the internal screen can be used.

The display setting shows Unknown Display as this image :

enter image description here

xrandr:

xrandr: Failed to get size of gamma for output default
Screen 0: minimum 1920 x 1080, current 1920 x 1080, maximum 1920 x 1080
default connected primary 1920x1080+0+0 0mm x 0mm
   1920x1080     77.00* 

Now if I want to switch from one monitor to another, I have to reboot my computer. What's wrong with the display and how can I fix the problem?

What's more, when I installed Ubuntu 20.04 first in Oct 2020 there was nothing wrong with the display and monitors. This problem appears after I re-install Ubuntu in Aug 2021. Could there be any problem with something that has been updated?

in flag
If you press [Fn]+[F8] are you able to switch monitors or get both working? This key combination tells the hardware where to send video data and operates independent of the OS
GKxx avatar
in flag
@matigo Thanks but nothing happens when I press this key combination.
ls flag
I've got exactly the same problem.
Score:0
im flag

my decision was sudo ubuntu-drivers autoinstall and reboot

jp flag
Hi there, thanks for your answer. Please provide some context about why you did this and what it actually does. Some links to information about the command would be great. This way people can decide if they want to try this in an informed way.
mangohost

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