Dual Monitor settings on Kubuntu 24.04.4 have gone haywire

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1

Ubuntu Support Template

Ubuntu Version:
Kubuntu 24.04.4 LTS

Desktop Environment (if applicable):
GNOME, KDE Plasma

Problem Description:
I was just working on my system with dual monitors:

Just doing routine stuff, developing a python command line script for my own use.

All of a sudden, both screens went nuts. I have different wallpapers on each screen and I can see that the one that should be on the external is on the laptop but extends into the BenQ. The screen resolution on the BenQ is wrong, and moving the mouse moves the whole display, not just the cursor.

Relevant System Information:
Lenovo ThinkPad P16 with NVidia RTX3500 graphics card. System has two monitors - the one with the laptop and a BenQ RD 240Q.

Screenshots or Error Messages:

What I’ve Tried:

changing settings in the System settings display

rebooting

turning monitor and laptop off and on

followed suggestions from AI as per this search:https://www.google.com/search?q=kubuntu+dual+monitor+settings+have+gone+bad&client=tablet-android-samsung-rvo1&hs=jYYV&sca_esv=46bf259341182f74&sxsrf=APpeQnuqajDTAYSnstR4JgXaERdLXRNnEA%3A1783552831224&ei=P9tOarmzDYyvur8Pmq_euAw&biw=1317&bih=650&oq=kubuntu+dual+monitor+settings+have+gone+bad&gs_lp=EhNtb2JpbGUtZ3dzLXdpei1zZXJwIitrdWJ1bnR1IGR1YWwgbW9uaXRvciBzZXR0aW5ncyBoYXZlIGdvbmUgYmFkMgUQABjvBTIFEAAY7wUyCBAAGIAEGKIEMggQABiABBiiBEjsU1CPSliPSnACeAGQAQCYAZEBoAGRAaoBAzAuMbgBA8gBAPgBAZgCA6ACpgHCAgoQABiwAxjWBBhHmAMAiAYBkAYIkgcDMi4xoAfMArIHAzAuMbgHlQHCBwUyLTIuMcgHEoAIAA&sclient=mobile-gws-wiz-serp`188

particularly

2. Clear Corrupted KScreen Cache

Sometimes the KDE display manager (KScreen) gets stuck on bad configurations. You can wipe the saved monitor layout and start fresh:

  1. Open your terminal.

  2. Remove the kscreen folder by running:
    rm -rf ~/.local/share/kscreen/

  3. Restart your system or log out of your session and log back in to force Kubuntu to re-detect your screens automatically. [1, 2]

3. Check Graphics Drivers

If your second monitor is not being detected at all, it could be a missing or malfunctioning driver: [1]

  1. Open the Driver Manager (or use the terminal command sudo ubuntu-drivers autoinstall).

  2. If you are using an NVIDIA card, open the NVIDIA X Server Settings and configure your resolutions and positions directly there. [1, 2]

The nvidia settings tell me that the Display Devices are “Unknown".

nvidia-smi output

Wed Jul  8 17:18:41 2026       
+-----------------------------------------------------------------------------------------+
| NVIDIA-SMI 580.159.03             Driver Version: 580.159.03     CUDA Version: 13.0     |
+-----------------------------------------+------------------------+----------------------+
| GPU  Name                 Persistence-M | Bus-Id          Disp.A | Volatile Uncorr. ECC |
| Fan  Temp   Perf          Pwr:Usage/Cap |           Memory-Usage | GPU-Util  Compute M. |
|                                         |                        |               MIG M. |
|=========================================+========================+======================|
|   0  NVIDIA RTX 3500 Ada Gene...    Off |   00000000:01:00.0  On |                  Off |
| N/A   42C    P8              4W /  115W |     198MiB /  12282MiB |      0%      Default |
|                                         |                        |                  N/A |
+-----------------------------------------+------------------------+----------------------+

+-----------------------------------------------------------------------------------------+
| Processes:                                                                              |
|  GPU   GI   CI              PID   Type   Process name                        GPU Memory |
|        ID   ID                                                               Usage      |
|=========================================================================================|
|    0   N/A  N/A            1629      G   /usr/lib/xorg/Xorg                      171MiB |
+-----------------------------------------------------------------------------------------+

The sudo ubuntu-drivers autoinstall command did not help and since the nvidia settings look wrong, I think I need to do a different fix with the nvidia drivers.

What might that be?

Before Posting:
:mag: Please check if similar issues have already been reported and resolved.

2

You have 2 possible options available to you:

  • use NVIDIA supported drivers,
            available here,        

or

  • build a specified version from source code,
            available from GitHub here
1 Like
3

Thanks. I tried reinstalling the nvidia driver - actually, I completely purged all the nvidia drivers, rebooted and installed the recommended version which is now

$ nvidia-smi Wed Jul 8 22:57:19 2026 +-----------------------------------------------------------------------------------------+ | NVIDIA-SMI 595.71.05 Driver Version: 595.71.05 CUDA Version: 13.2 | +-----------------------------------------+------------------------+----------------------+ | GPU Name Persistence-M | Bus-Id Disp.A | Volatile Uncorr. ECC | | Fan Temp Perf Pwr:Usage/Cap | Memory-Usage | GPU-Util Compute M. | | | | MIG M. | |=========================================+========================+======================| | 0 NVIDIA RTX 3500 Ada Gene... Off | 00000000:01:00.0 On | Off | | N/A 43C P8 5W / 115W | 198MiB / 12282MiB | 0% Default | | | | N/A | +-----------------------------------------+------------------------+----------------------+ +-----------------------------------------------------------------------------------------+ | Processes: | | GPU GI CI PID Type Process name GPU Memory | | ID ID Usage | |=========================================================================================| | 0 N/A N/A 1629 G /usr/lib/xorg/Xorg 171MiB | +-----------------------------------------------------------------------------------------+

(my apologies for the above mess. I cannot figure out how to format it correctly. I also tried to show it as a screenshot but your site wouldn’t accept the upload of a screenshot. Maybe someone can reformat it.)

However, reinstallation of the driver has not solved the problem.
All is as it was initially:

Reinstalling the driver made no difference in this situation. The system is only borderline usable.

I’m still trying to understand what the hell happened. As I was sitting there doing normal stuff, no heavy use, no gaming, no GPU intensive stuff, the screens just went crazy.

I guess I’m looking for a way to do on the command line what the Kubuntu gui System Settings display page does.

4

That sounds more like you inadvertently triggered (via keyboard shortcut) some accessibility mode, e.g. a magnifying glass.

By the very nature of “Ai” it is very likely that people doing the same search may receive a different “answer”, because the “Ai” in the meantime has “learnt” new stuff.
Just say what you did and don’t just refer to some nondescript instructions.

5

I followed those instructions, as they were written there. That is why I presented it that way. That IS what I did! Please don’t assume I’m a moron. I’m not in the mood! Following those instructions made no change in the situation. They didn’t make anything worse. They didn’t make anything better.

I ALSO TOLD you what I did following that: I purged the nvidia drivers and reinstalled the recommended driver: nvidia-driver-595-open. And rebooted.

This ALSO didn’t make any improvement.

I have noticed one other thing of interest:

In the Kubuntu system settings Displays tab, I can see representations of both screens in the display. One is labeled “Built-In Screen”. The other is labeled “BenQ RD240Q”. As it should be. However, the interface has a button labeled “Identify”. It identifies monitor that is selected. Whether the Built-In Screen or the BenQ RD240Q is selected, pressing “Identify” shows the identity “BNQ BenQ RD240Q”. It seems from this that the system is confused as to which monitor is which.

6

I should also mote that the system presented me with a bunch of updates that it said were available, two days ago. I installed these. I don’t remember offhand what they all were. Some were from Lenovo. Others from Ubuntu. If someone can point me to the log of what was installed in that process, it’s possible that one of them may be the culprit, although it isn’t likely, since the appearance of the problem was two days later.

7

The point is that those instructions are in flux. Nobody can say what they will be in half an hour, tomorrow…

Far be it from me.

8

/var/log/apt should contain all the logs from DEB package actions. snap changes for snaps.

9

It doesn’t matter for the purposes of this issue whether the instructions are in flux or not or whether following AI suggestions is wise or not.

The instructions I followed were exactly what i posted. It doesn’t matter where they came from. And they had no effect one way or the other.

They are not the issue.

I would draw anyone’s attention to the detail I posted above in which the “Identify” button on the System Settings App’s Monitors and Displays tab incorrectly identifies the Built In Monitor as the external monitor! It seems that all the weirdness I suddenly started experiencing today may be related to that misidentification.

And I would like help from anyone who might know how to diagnose it further.

10

Here’s another detail that may or may not be relevant:

I ran the nvidia-settings command from the command line. It showed several errors, one of them critical, before successfully showing the app:

$ nvidia-settings

(nvidia-settings:13498): GLib-GObject-CRITICAL **: 00:36:04.203: g_object_unref: assertion 'G_IS_OBJECT (object)' failed

ERROR: The requested operation is not available on target device


ERROR: The requested operation is not available on target device


ERROR: The requested operation is not available on target device


ERROR: The requested operation is not available on target device

** Message: 00:36:04.342: PRIME: Requires offloading
** Message: 00:36:04.342: PRIME: is it supported? yes
** Message: 00:36:04.373: PRIME: Usage: /usr/bin/prime-select nvidia|intel|on-demand|query
** Message: 00:36:04.373: PRIME: on-demand mode: "1"
** Message: 00:36:04.373: PRIME: is "on-demand" mode supported? yes
11

Thanks.
I’ve looked through there and I don’t see anything that stands out to me. It all looks like fairly mundane stuff.

The updates I remembered which now seem suspect were firmware updates from Lenovo. I don’t know where those might be logged. But even these did not immediately result in the messed up screens.

12

Another point of possible interest:

$ xrandr
Screen 0: minimum 320 x 200, current 4480 x 1600, maximum 16384 x 16384
eDP-1 connected primary 1920x1200+0+0 (normal left inverted right x axis y axis) 344mm x 215mm
   2560x1600    165.00 +  60.00 +  60.00  
   2560x1440     60.00  
   2048x1536     60.00  
   1920x1440     60.00  
...
   320x175       60.00  
HDMI-1-0 connected 2560x1600+1920+0 (normal left inverted right x axis y axis) 518mm x 324mm
   2560x1600     59.99*+
   3840x2160     59.94    50.00    29.97    25.00    23.98  
   640x480       75.00    59.94    59.93  
...
DP-1-0 disconnected (normal left inverted right x axis y axis)
DP-1-1 disconnected (normal left inverted right x axis y axis)
DP-1-2 disconnected (normal left inverted right x axis y axis)
DP-1-3 disconnected (normal left inverted right x axis y axis)

I have no idea what this output means but the first line looks suspicious:

Screen 0: minimum 320 x 200, current 4480 x 1600, maximum 16384 x 16384

what does this 4480x1600 mean here? That’s not a dimersion that pertains to either monitor but 4480 is the sum of 2560 and 1920, the horizontal dimensions of the two monitors.

13

That means that your (virtual) resolution somehow got set to that value, which explains why your mouse motions moves the whole desktop. Say your native resolution is 1920x1080. You can only see what the native resolution allows, so the desktop must pan the canvas to show what’s hidden outside the “looking glass” of 1920x1080 dimensions.

I still think you should go looking for keyboard shortcuts that might do that; you might have pressed one inadvertently. I’d start with “Accessibility” because this has all the hallmarks of screen zoom.

14

A further experiment along these lines shows that the problem is not just with System Settings Displays and Monitors but the whole screen sizing system is hosed:

I turned the system off and unplugged the second monitor. Upon restarting,

  • all content is still too big for the screen. It is as if the system thinks the screen is bigger than it is. Whatever content is displayed is bigger than it should be.
  • As I noted in the original post, moving the mouse does move the cursor but also “moves the screen”. That sounds absurd and it is. I’ve never seen anything like it. It seems that the dimensions of the monitor are smaller than the dimensions of what the system thinks the screen size is. Moving the mouse left, for example, not only moves the cursor left but also moves the displayed content right allowing content that was previously “off the left edge” to appear.
  • With only one monitor connected, System Settings → Displays and Monitors does not show the “Identify” button. But if I plug the second monitor back in, System Settings → Displays and Monitors once again shows the “Identify” button, but whichever monitor I select now identifies itself as the Built-In Display.
15

Look where? I never have heard of such a keystroke.

I can’t imagine that pressing such a keystroke, whatever it might be, would have effects that would persist across reboots, and video driver uninstall-reinstalls.

16

That means that your (virtual) resolution somehow got set to that value, which explains why your mouse motions moves the whole desktop. Say your native resolution is 1920x1080. You can only see what the native resolution allows, so the desktop must pan the canvas to show what’s hidden outside the “looking glass” of 1920x1080 dimensions.

This makes sense and may explain what I’m experiencing.

Regardless of how it may have happened, how can I set it back to what it’s supposed to be. Is there some xrandr command that would fix this?

17

By the way, I am now making these posts from my Android tablet. Things have gotten so out of whack on the Lenovo that it is impossible for me to scroll far down enough to see the blue reply button at the bottom. :frowning:

18

I can only tell you how it works in GNOME, but KDE must have something very similar:
Open “Activities” (press and release Super aka ⊞ Win and type keyboard shortcut. That should direct you to correct sub-menu of GNOME Settings.

I don’t know if such settings are supposed to stick across reboots but it seems not at all unreasonable that visually impaired persons would want that to be the case.

There might be other explanations, but that was my first impulse when reading your description of the issue. It happens to me all the time that I accidentally press a key combo with Super, when I really want an Alt shortcut. But I’m also using neither GNOME nor KDE, so that’s where the similarities end.

19

I looked and found one Accessibility keyboard shortcut - but it was for turning Screen Reader on and off. So I don’t think that’s the answer.

20

I said start with accessibility. :wink: I cannot currently run my Ubuntu 26.04 Desktop VM, because it’s in a (purposely) broken state, but I seem to remember that there were “Zoom” and “Magnifier” shortcuts. Where they are, I don’t know.