Beyond this I am not sure what anyone could suggest. If using xrandr from Konsole does not work start looking for other command line solutions. If you find a way to do this then you could write a script to do it. Perhaps an internet search of “Linux command line how to set laptop screen brightness?”
Possibly updating the BIOS firmware on the notebook might help if there is such an update.
That is great. I do wish we had better answers for this laptop screen brightness control issue but we don’t. The search continues for a solution or some code that would resolve this favorably for all Linux users. IMO the real culprit is either the BIOS firmware or the hardware manufacturers.