Hello,

I'm using Kubuntu 20.04. I have an issue with the multiple screen setup. I have the laptop's internal display and one external display on a DP connection.

In about 1 out of 10 boots, maybe even more often, the screens are reversed and there is no panel no nothing. The background images load (and the weather appears but it's grayed out) and I can see the mouse cursor moving, but right clicking doesn't do anything. The only thing that works is the power off button. I get the shutdown menu, and I can reboot then. Sometimes more than one reboot is necessary.

When this happens the boot takes a lot longer then usual. Once the external monitor didn't load the background. Once it loaded but it was the wrong resolution. So I suspect there's something wrong with detecting it.

Nothing I tried worked. I tried using arandr and removed kscreen. The issue is still there. I tried deleting all the plasma screen related config files in ~/.local and ~/.config. It made no difference.

Any ideas?

Thanks.

I have the same setup, one laptop screen and one external via DP, but I have never seen this happening here, so maybe this is specific to your setup and something else is interfering. Did you try with a new user?

Thank you for the suggestion to try with a new user. I did that, and as far as I can tell, the issue is not there.

One thing I noticed: the system had started with the old user, and the issue appeared; I decided to just log out (not a complete reboot) and try the other user. Now the issue was there as well. But it never happened if I logged in with the new user first. I tested things using automatic login with each user and rebooting, as I always use automatic login.

Now, I would rather not have to go through the whole reinstalling and setting up everything. So, do you have any tips on how to pinpoint the issue?

P.S. Another thing I noticed: when things go wrong, the monitors are inverted left-right, not the way I set them up.

P.P.S. I ended up using the new account's files as a basis, and copied over the various configuration files I felt made my system complete. I suppose I could have done it another way, by copying over the new account's files over the old one, but the way I did it felt more effective, with less of a risk of things going bad again.

P.P.P.S. The issue came back after a few months. The new user trick didn't work this time. Because the issue appeared to manifest during boot, starting with the KDE logo, I assumed it might be an SDDM resolution problem. Going down that route didn't yield results. I then recalled that right after I installed Kubuntu 20.04, I had issues with the grub menu GRUB not being visible. The solution then was to uncomment GRUB_TERMINAL=console in /etc/default/grub and run "sudo update-grub". I looked inside that file, and that section was now commented again. I suppose it happened atutomatically when GRUB received an upgrade at some point? I edited the file again, and I've had a decent number of reboots without the resolution problem. I cannot comment with regards to the mechanism at work, but I can report the facts in case anyone ends up reading this post. Hopefully, it's a real, lasting solution.