Hello,
I have two laptops that are set up equally, both with kubuntu 25.10 updated via backports to kde 6.5.3, and on kernel 6.17.0-7-generic.
One of the laptops is able to control the brightness of the external displays via the brightness widget in the tray bar just fine. Changing the setting there changes the actual hardware brightness in the external monitor (as verified by checking in the monitor itself).
The other laptop though, while having the same options in the widget, only seems to apply a weird black-bluish shader/filter to the screen, without modifying its actual brightness (and it doesn’t look good really).
Both laptops connect to these screens in the same manner (display port). What could possible make one be able to do it correctly, while the other simulates it?
sorry, I don’t follow. It’s the same cables and the same monitors, I alternate with these laptops when they are plugged.
That is interesting indeed.
My first instinct would be to connect the one that doesn’t work switched off, turn the monitor on and then boot just to see what happens.
try the other cable with the difficult monitor.
My first instinct would be to connect the one that doesn’t work switched off, turn the monitor on and then boot just to see what happens.
I’ve done that multiple times, no changes.
try the other cable with the difficult monitor.
Done that already, with several different cables too.
Could the video card have anything to do here? both have nvidia cards but one is rtx3080 (the one that doesn’t do the trick) and the other is rtx 2070 (the one that works). Both with same driver version.
is it 580.105.08
because that’s what it should be for both according to the nvidia website.
It’s 580.95.05, latest from the ppa on ubuntu.
what is the output of ubuntu-drivers devices
On the machine that doesn’t work (let me know if you want it from the other too)
== /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0 ==
modalias : pci:v000010DEd0000249Csv000017AAsd000022E4bc03sc00i00
vendor : NVIDIA Corporation
model : GA104M [GeForce RTX 3080 Mobile / Max-Q 8GB/16GB]
driver : nvidia-driver-580-server-open - distro non-free
driver : nvidia-driver-580-open - distro non-free recommended
driver : nvidia-driver-580-server - distro non-free
driver : nvidia-driver-580 - distro non-free
driver : xserver-xorg-video-nouveau - distro free builtin
Now that I see this, I don’t remember if I have the -open ones in the other laptop 
EDIT: checked, hmm, the non working has the “open” drivers, the other has the regular non-open ones. Could this be it?
likely the difference is due to the different drivers, yes.
i would go with the one that shows as recommended for each device and just live with the diferences until it gets fixed.
Yeah, sounds good. I don’t mind that much either, it was mostly curiosity.
Thanks.