Ubuntu 20.04 Intel HD 615: No Brightness control or no Boot / Stuck on Boot Screen

I just did a fresh install of Ubuntu 20.04 on my dell xps9365 with intel HD615 graphics & 4k display

1. First boot:

In the Settings > About I can see that it is using the Mesa Intel HD Graphics 615 (KBL GT2) At this point i also have a slider to adjust my brightness.

2. First REboot:

At the first reboot its not working anymore. It keeps hanging at splash screen. So i did some searching and added nomodeset to my grub file before booting. It Boots up! But now i don't have my brightness slider and i see it is using the llvmpipe drivers instead of the Mesa Intel HD Graphics 615 (KBL GT2).

I tried to change GRUB_CMDLINE_LINUX_DEFAULT to different variants:

quiet splash nomodeset video.use_native_backlight=1
quiet splash nomodeset acpi_backlight=video
quiet splash nomodeset acpi_backlight=vendor
quiet splash nomodeset acpi_backlight=native

nomodeset video.use_native_backlight=1
nomodeset acpi_backlight=video
nomodeset acpi_backlight=vendor
nomodeset acpi_backlight=native

But all give the same result: llvmpipe drivers and no brightness control.

When i was reading trough some post this is what i learned also: nomodeset disabled the drivers during boot, so you don't have a fancy splash screen. Once the machine is booted it would load the proper drivers. But for some reason it doesn't seem to be working for me.

Can someone please help?

I found the solution myself!

in the file : /etc/default/grub

change this line:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

to

GRUB_CMDLINE_LINUX_DEFAULT=""

and then

sudo update-grub