ROG Zephyrus G15 does not work on ubuntu with exernal screen

Good morning everyone,

So I installed Linux 20.4 Ubuntu Distro on my G15 laptop.
Link to the laptop model: ROG Zephyrus G15 GA503 | 2021 ROG Zephyrus G15 | Gaming Laptops|ROG - Republic of Gamers|ROG Global

Installed ubuntu with safeboot compatibility on the M2. SSD after dedicating 200 gigs for linux.
So the problem lies with that even though I have the IGPU mode disabled in windows and Installed 3rd party drivers my ubuntu does not work properly.

The HDMI port does not work and everything on my main screen is laggy which probably is because everything runs on the internal AMD IGPU. I also have to use nomodeset constantly when booting to Ubuntu otherwise It freezes on the logo screen after GRUB.

Can anyone maybe explain how I could fix this problem? Do I have to install a specific RTX 3060 Nvidia driver for it or do I have to change something else in Bios?

Thank you in advance for all your help and I wish you all a very nice day!

Kindest regards,