Consider the steps below as my personal notes if I ever need to factory reset my laptop. There are some gotchas and little quirks and mistakes in the documentation online. Articles will mention "if Intel RTS is activated and ..." but what I'll describe here is what worked for me. If you get the same laptop as me, these steps should get you up and running without any fuss. Good luck!

3-step guide to installing Ubuntu 20.04 side-by-side with Windows on a new Dell XPS laptop.

1. Disable Windows disk encryption
2. Disable Intel RTS
3. Install wifi drivers

1. Disable Windows disk encryption

You can follow the instructions on Ubuntu's help forum here:
https://discourse.ubuntu.com/t/ubuntu-installation-on-computers-running-windows-and-bitlocker-turned-on/15338. Pretty straight forward. In a nutshell, go to Windows settings > Encryption, disable encryption, restart computer. Done. Next.

2. Disable Intel RTS

Follow most of the instructions here https://help.ubuntu.com/rst/.

Start by changing registry values for iaStorV & storahci as documented.

Next, skip the rest of the instructions and follow nitram-mural's advice here: https://discourse.ubuntu.com/t/ubuntu-installation-on-computers-with-intel-r-rst-enabled/15347/90:

The solution was to set the safe mode (safeboot) manually. Right after the regedit changes:

• With a cmd with admin rights (windows search: cmd, then right click, run as admin):
• bcdedit /set {current} safeboot minimal
• Reboot to BIOS.
• Change from RAID (RST) to ACHI in the BIOS.
• Reboot.
• Windows enters safe mode correctly and setups the “new” hardware using the temporarily enabled drivers. New hardware connected sounds and all.
• Then before restarting, revert the safeboot mode: bcdedit /deletevalue {current} safeboot
• To go back to normal boot.

3. Install wifi drivers

When you'll first boot on Ubuntu you won't have any default drivers for the wifi card. To get the below packages you can tether from your phone using bluetooth.

sudo apt update -y
sudo apt install linux-oem-20.04

I had first install build-essential but it shouldn't be necessary.

Alright folks. Hope it helps!