[Samsung NP530] Backlight on dual graphics machine, notification

I'm having backlight issue on my machine.
When I press Fn+(backlight up)/(backlight down) I get the notification that backlight is changing but no actual effect on the screen. I tinkerd around and I found that I can change the value in /sys/class/backlight/acpi_video0/brightness by echo [value 0-95] > /sys/class/backlight/acpi_video0/brightness. So I can easily write a .py script to fix it. BUT..
I do have some concers:
I can only change this value as a su so how should I approach this being logged in as a 'normal' user?

adding one of these kernel parameters to grub CMDLINE could fix your issue.

acpi_backlight=native acpi_osi=Linux
acpi_backlight=vendor acpi_osi=Linux
acpi_backlight=video acpi_osi=Linux
or just acpi_osi=Linux on its own

sudo nano /etc/default/grub

edit following line like this: (each parameter separated by single space.)

GRUB_CMDLINE_LINUX_DEFAULT="acpi_backlight=vendor acpi_osi=Linux <leave other parameters as they are>"

CTRL+X, then Y, then ENTER (to save/exit)
sudo update-grub
no errors? reboot and test.

if you need to try other parameters, just be sure to update-grub after each change for it to become effective at grub/boot

I've tried all 4. After every change sudo update-grub like you advised. Unfortunately, none of them worked.

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