Installing Ubunut 20.04 on several models of ASUS lpatops (and other brands) using NVidia video can have several issues. The first issue I noticed was the PCIE errors, the next error is the purple screen after login.
To resolve these issues boot into the BIOS Setup and turn off Fast Boot and disable any Secure boot options. Once this is done boot normally from your boot CD or USB Stick; follow the prompts and install Linux with the options you want.
Once Linux is installed we need to add parameters to the grub config and update grub. The steps are outlined below:
1) Boot from the Ubuntu install media and select Try Ubuntu.
2) Open a terminal session by pressing CTRL-ALT T or selecting from the menu.
3) In the terminal window login as the super user by typing “sudo su -” and pressing enter.
4) Next we will mount the file system and change the root, type the following commands:
mount -t ext4 /dev/sda2 /media <- this assumes your linux is installed on sda2 and the mount point is /media
mount –bind /dev /media/dev &&
mount –bind /dev/pts /media/dev/pts &&
mount –bind /proc /media/proc &&
mount –bind /sys /media/sys
5) Edit the grub config file to include nomodeset and pcie_aspm=off.
6) Change directory to /etc/default
7) run “vi grub”, use vi to edit the file, change the GRUB_CMDLINE_LINUX_DEFAULT line. Immediately after “quiet splash” add “pcie_aspm=off nomodeset”. Save the file/
8) Run update-grub, make sure you don’t see any errors.
9) Reboot and login. Everything should be working but the screen resolution is likely 800X600. To fix this we need to remove “nomodeset”.
10) Change to /etc/default, edit grub and remove “nomodeset”.
11) Run update-grub, make sure there are no errors reboot.
12) Login and everything should be working with no errors.