After upgrading Ubuntu 18.04 to 20.04.1 I get the following visual artifacts on screen:
The location where the artifacts appear seems random, especially for the dark "noise like" pixel areas. The vertical green bar seems to always appear at more or less the same location.
The computer is an Intel NUC, with Intel Core i3-6100U CPU and Mesa Intel HD Graphics 520 (SKL GT2). This computer does not have a monitor attached to it. I connect to it via Remmina (VNC). The shown artifacts were not there when it ran Ubuntu 18.04. The artifacts disappear when I change the wallpaper. However, after reboot are the artifacts back again, until I again change the wallpaper. This issue is not caused by connecting remotely to the NUC: it is also visible when I temporarily connect a monitor to the NUC itself. I do not know the correct words for these artifacts. And have therefore not been able to find any solutions or hints while searching online.
How can I solve this issue?
I had basically the same problem, though the artefacts looked a little different. It seems to be caused by having old Intel graphics drivers installed, and removing those fixed the problem for me and a number of other users: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1867668
Summary:
Remove the drivers:
sudo apt remove xserver-xorg-video-intelRemove the corresponding X conf file, if it exists: it seems to be located either at
/etc/X11/xorg.conf.d/20-intel.confor/usr/share/X11/xorg.conf.d/20-intel.conf.So run e.g.
sudo rm /etc/X11/xorg.conf.d/20-intel.conf(You might want to make a backup first, in case something goes wrong.)
Reboot
I solved this issue by installing a HDMI plug to the NUC's HDMI port. Then I followed the recommendations from https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1867668 (which was pointed out to me by Ozzin). After reboot the HDMI plug is detected and the visual artifacts have disappeared.