I have a problem with one particular monitor flickering on KDE Neon 5.18. Three monitors in total, only one has the issue.

The problem exists on every system that I used, which is Windows 10, Ubuntu 18.04 (with Gnome and later Plasma) and finally KDE Neon. On each one of them there was a simple solution - change the screen refresh rate. Windows 10 offered two options: 60Hz, 59Hz; Ubuntu: 59.95Hz, 59.88Hz. This worked both on Gnome and later on manually installed Plasma desktop (though display settings app stayed the same as on clean Ubuntu with Gnome). Finally, I decided I fancy KDE products so much that I should give KDE Neon a try. Everything works perfectly but for this one issue.

In display configuration, I don't have option to change refresh rate on anything besides 60Hz:


This is what it looked like on Ubuntu:


Obviously I tried every possible Compositor configuration. It helps to some extent or for some time, but then, out of the blue, the screen starts flickering again. Changing the screen refresh rate on Windows 10 and Ubuntu was the ultimate solution, the screen never flickered once this setting was changed.

I also tried this:
https://askubuntu.com/questions/672007/ ... plasma-5-4

My system and graphic card builds:



If no solution will be found, please tell me, is it possible that on Kubuntu I will be able to change the refresh rate the same way as on Ubuntu? I would like to have Ubuntu + Plasma on my computer, exact distribution is a secondary matter.

Thank you in advance

Seems like Compositor is the source of the problem. After disabling it, the screen stopped flickering (at least for now), though I lost some animations, for example during virtual desktop switch.

After installing Plasma desktop on Ubuntu manually there was no Compositor hence no flickering.

To disable Compositor open it from Application Launcher, untick "Enable compositor on startup" and restart.

UPDATE
Never mind, flickering still occurs.

if the flickering occurs with this monitor on all systems, then how about checking your monitor cable? Video and HDMI cables can be tricky beasts and screen flickering should always trigger a hardware check first.

Indeed I have a somewhat weird situation with monitor cables. My graphics card has 1 HDMI port and 3 DisplayPort. None of my monitors has DisplayPort socket, so my main monitor is connected straight via HDMI and the other two have adapters DVI - DisplayPort (the problematic one), VGA - DisplayPort. But I don't think the adapter is the issue because with my previous graphics card, the monitor was connected straight via DVI and the problem still existed, although I used only Windows, so it was easily fixed as described before.

I tested another desktop - Xfce and just like with Gnome - there are 2 different refresh rate options, hence no problem.


So the main issue I am wondering about is why Display Configuration module on KDE Neon presents only one option.

UPDATE

The issue seems to be SOLVED. I changed the refresh rate using xrandr program. For the past couple of days, flickering didn't occur.
Thanks to: https://bbs.archlinux.org/viewtopic.php?id=226289

For other rookies like me:
1. Type xrandr into the command line and observe display name whose refresh rate you want to modify (1), its target resolution (2) and available refresh rates (3). Notice that the one with asterix (*) is the current one.



2. Change the refresh rate with following command:


3. Confirm it was changed: