laptop - Display brightness cannot be adjusted 18.04

I have recently installed Ubuntu mate 18.04 on my XPS 15 9560. I cannot adjust the display brightness through any means. I have tried the following:

1. Set the acpi_backlight=vendor in boot parameters


2. used xbacklight, which gives the following results

.

xypnox@xypnox-xps:~$ xbacklight -set 50
No outputs have backlight property

also I followed another question at xbacklight: No outputs have backlight property - No /sys/class/backlight folder, and the output for sudo find /sys/ -type f -iname '*brightness*' is

xypnox@xypnox-xps:~$ sudo find /sys/ -type f -iname '*brightness*'
/sys/devices/platform/dell-laptop/leds/dell::kbd_backlight/brightness_hw_changed

/sys/devices/platform/dell-laptop/leds/dell::kbd_backlight/max_brightness
/sys/devices/platform/dell-laptop/leds/dell::kbd_backlight/brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::capslock/max_brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::capslock/brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::numlock/max_brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::numlock/brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::scrolllock/max_brightness
/sys/devices/platform/i8042/serio0/input/input4/input4::scrolllock/brightness
/sys/module/video/parameters/brightness_switch_enabled
/sys/module/i915/parameters/invert_brightness

I have finally found the solution to the problem. There display drivers for Ubuntu did not work out of the box for me. I started fresh from a 18.04.1 release and used nomodeset to boot into the live USB. Obviously, I could not set the brightness. I installed regularly and rebooted.

I installed the latest nvidia drivers from the ppa: https://launchpad.net/~graphics-drivers/+archive/ubuntu/ppa

Then I restarted the system and also added the boot parameters acpi_rev_override=5 nouveau.runpm=0.

After the restart the desktop worked fine and I could change between the nvidia and intel graphics and could set my brightness.

Also, updating the kernel did not solve the problem for me.