We need to update the BIOS to the latest version, make some changes to the BIOS configuration and we need to flash a USB installer with the latest version of Elementary OS (more on that later).
We will need a USB stick with at least 2GiB of space.
I updated the BIOS to 1.5.0 (the latest version currently available). I formatted a USB stick to FAT32 and put the BIOS update executable onto the USB stick. Then while powering on the laptop, I pressed F12 to access the boot menu and chose the option BIOS Flash Update - which allowed me to select the XPS9570010500.EXE and apply it without having to boot into Windows.
In the Dell XPS BIOS (accessed with F2 at startup) I set the following options.
- General > Boot Sequence > Boot List Option > check UEFI
- System Configuration > SATA Operation > check AHCI
- Secure Boot > Secure Boot Enable > uncheck Secure Boot Enable
- Secure Boot > Disable
Whilst creating the USB in Rufus, I used GPT/UEFI mode and wrote the image in "DD" image mode.
You may be able to use Etcher on a Linux system in place of Rufus.
I had to write the USB installer in DD mode with Rufus. I was only able to get the Dell XPS 15 to boot from a USB stick in the left-hand USB port!
At power on F2 will access the BIOS settings, whilst F12 will provide you with a one-time boot menu.
The Elementary OS installation was performed as usual from this point onward, creating user accounts and encrypting the disk.