SUMMARY

Since upgrade to Kubuntu 24.10 some days ago, the output to my screen, in fact hdmi 42 inch tv screen, is dimmed. 
I tried various way to corrrect that without any effective effect. 
If i boot on another distribution my video output is as before, ie clean and clear. 

If i try to go in the right tray "luminosite et couleur" so probably "luminence and color" in english, i only have the option to configure night luminance and color, and if so thigs get worse. 
We don't have any control for nomal lominance (contrast) and dark luminance (brightness) in these settings. 
So the are not any way to manually correct what have been lowered in this version. 

STEPS TO REPRODUCE
1. Upgrade from Kubuntu 23.04 to 23.10
2. After upgrade problem is always there, no correction possible
3. 

OBSERVED RESULT

Low contrast (higer white maximum luminance) and higher brightness (lower luminance level, near the black in an image)  than needed. 
No adjusment possible from what i found. 

EXPECTED RESULT

I expect to be able to adjust contrast and brightness in normal mode, not only night mode. 
And i expect it to be as before the upgrade, when it needed no adjusment from the OS papameters, only on my tv screen. 

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
(available in the Info Center app, or by running `kinfo` in a terminal window)
Linux/KDE Plasma: kubuntu 24.10 
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION
I run my Kubuntu on an old Dell optiplex 9020, with on board graphic card and HDMI output on a tv screen.
Setup ok with a Win boot or another distribution boot.
Problem came from new version of plasma on the Kubuntu 24.10 upgrade.