Dell XPS 7390 stuck in BIOS setup after setting GRUB_DEFAULT="2"

[TheMainMan]

Hi everyone,

Story:
I have a Dell laptop XPS 7390 Developer Edition, with Ubuntu 18.04 pre-installed. Since 18.04 is no longer supported, I decided to upgrade it to 20.04, using the Software Update. After successful upgrade, Ubuntu 20.04 does not show any network adapter in the Network settings, the Wifi settings is hidden too (only appear when I intentionally search the setting name). ip add command shows only lo1 (loopback) interface. I looked up and many sources state that the Intel(R) Killer(TM) Wi-Fi 6 AX 1650, 2x2, 802.11ax, Bluetooth (R) wireless card of the XPS is not compatible with the Linux kernel. So, I changed the default kernel by editing the GRUB_DEFAULT in the /etc/default/grub. After that, I reboot the laptop and it stuck in the BIOS setup forever. Even I manually select the boot option of Ubuntu, it did not let me boot into Ubuntu. Now, I am stuck in the BIOS setup.
487543534_564245510019105_6064296441913734559_n.jpg

What I've tried:

• Follow the guides to boot into Ubuntu using GNU GRUB - have not worked so far, faced many kinds of error. References:
  
  • https://www.youtube.com/watch?v=ZhxBJ3yh2OY
  • https://www.youtube.com/watch?v=LFj_yqk6AUI
  • https://www.howtogeek.com/887757/how...the-grub-shell
  
  
• F12 while booting to enter the boot option in order to manually boot into Ubuntu - did not work, it reboots the laptop and enters the BIOS setup again

What I want:

• Escape the BIOS setup and boot into Ubuntu
• After that, gain the network connectivity back

Any information and questions to remedy this situation are appreciated.

Thanks,