This page describes Debian on the Dell XPS 13 9370 released in January 2018
# dmidecode | grep "Product Name" Product Name: XPS 13 9370 Product Name: 0F6P3V
Before you install Debian, you should upgrade to the latest BIOS update from Dell.
Power on your notebook and press F12 to get into the BIOS. Choose the "BIOS Flash Update" option. This will show you the revision of your current BIOS.
Dell XPS 13 9370 support page and look for "BIOS". If there's a new BIOS update, download the XPS_9370_x.y.z.exe file and then put it on a USB stick (formatted with VFAT). Put the USB stick into your Dell and choose "Begin Flash Update" to update your BIOS. If you already have Debian installed in your machine, you can copy the file XPS_9370_x.y.z.exe in the boot/ partition, reboot your computer and install it from there.
You have to change some BIOS settings before you can install Debian. Press F12 again when starting your notebook to get into the BIOS.
Choose the first option, BIOS Setup. You must remove Secure Boot to install Debian since Debian currently doesn't support secure boot.
When you connect the USB stick and start your Dell notebook, the installer menu should automatically come up. If not, enter the BIOS and change the boot order.
You can choose "Graphical install" or "Install" (the text-based installer). In both cases, the fonts are quite hard to read. There are some bugs on this already (e.g. 816111).
The wifi card is supported but requires non-free firmware. You'll get a message about missing firmware files
You can download the "Unofficial non-free images including firmware packages" Debian installer : http://cdimage.debian.org/cdimage/unofficial/non-free/cd-including-firmware/
You can get the firmware-atheros .deb file and extract it to a USB stick.
You need at least the version 20170823 of firmware-atheros, it's available from stretch-backports.
3a:00.0 Network controller: Qualcomm Atheros QCA6174 802.11ac Wireless Network Adapter (rev 32)
After the installation, configure the non-free repository in APT and install the firmware-atheros package in order to get firmware updates for the wifi card.