Computer gives no signal to external HDMI monitor after upgrading to KDE Plasma 6.4

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1

Hi everyone,

Since the upgrade to KDE Plasma 6.4, I cannot connect my external monitor to my laptop over HDMI. When I plug the HDMI cable in, I do get the set of options to extend right, unify, etc. I click one of them but nothing happens after that. The external monitor says it is not getting a signal and works with other devices.

I do have an NVIDIA GPU in the laptop, see the terminal output below, but it doesn’t show up in the info centre.

niels@fedora:~$ lspci | grep -i vga
00:02.0 VGA compatible controller: Intel Corporation CoffeeLake-H GT2 [UHD Graphics 630]
01:00.0 VGA compatible controller: NVIDIA Corporation GP107GLM [Quadro P1000 Mobile] (rev a1)

Before upgrading to KDE 6.4, when I booted the laptop it said it couldn’t find the NVIDIA kernel module and is falling back to NOUVEAU. But then in the info centre it still did not show the NVIDIA GPU and it also didn’t show up in games. The boot message is not showing after the upgrade to KDE 6.4.

Anyone know what is going on? I don’t know how to even start troubleshooting this. There was no problem before upgrading to KDE 6.4.

Output of info centre:

Operating System: Fedora Linux 42
KDE Plasma Version: 6.4.0
KDE Frameworks Version: 6.15.0
Qt Version: 6.9.1
Kernel Version: 6.14.11-300.fc42.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 12 × Intel® Core™ i7-8750H CPU @ 2.20GHz
Memory: 16 GiB of RAM (15.3 GiB usable)
Graphics Processor: Intel® UHD Graphics 630
Manufacturer: HP
Product Name: HP ZBook Studio G5
System Version: SBKPF
2

It is worth checking for messages in dmesg and the user and system journals.
Have a look at the output of kscreen-doctor -o.
It may be an issue in the kernel, likely you got a new kernel with you updated to kde 6.4.0.
Try booting the previous kernel to see if the issue goes away.

3

Same issue. Can’t confirm it was plasma 6.4 specifically because i rarely use HDMI but that sounds like the most likely cause.

kscreen-doctor -o only shows my integrated display, whether the cable is plugged in or not.

As suggested by @barryascott , there was indeed a kernel update at the same time. However, booting into 6.14.11 instead of 6.14.9 did not solve the issue.

CPU: 13th Gen Intel(R) Core(TM) i9-13980HX (32) @ 5.60 GHz
GPU 1: NVIDIA GeForce RTX 4060 Max-Q / Mobile [Discrete]
GPU 2: Intel Raptor Lake-S UHD Graphics @ 1.65 GHz [Integrated]
OS: Fedora Linux 42 (KDE Plasma Desktop Edition) x86_64
Host: ROG Strix G814JV_G814JV (1.0)
Kernel: Linux 6.14.11-300.fc42.x86_64
Display (NE180QDM-NZ2): 2560x1600 @ 60 Hz in 18" [Built-in]
DE: KDE Plasma 6.4.0
WM: KWin (Wayland)

I have used the nvidia drivers in the past and migrated back to nouveau, which I believe I did properly.

4

What happens if you plug in the monitor first, and then power on the monitor, followed immediately by powering on the PC?

I have to follow this exact process with Fedora and an LG monitor.

5

I am having a similar issue.
But mine is a desktop with an AMD gpu that does still output to a displayport monitor, but not to a TV via HDMI, (or the aforementioned monitor via HDMI either fwiw)
Perhaps of note that the system does still recognise the displays, but the displays give ‘no signal’
Interestingly another laptop that is running the same up to date fedora version can still output to HDMI (intel GPU iirc).

I also noticed two new strange behaviours. The DP output is now capped at 165fps whereas it should go up to 180. And the audio bugs out if I try to display both screens side by side.

EDIT: booting with the previous kernel version from the grub menu made all three of these issues dissapear.