Dell XPS 7590 Ubuntu 18.04 - No WiFi Adapter found

The Dell XPS 7590 ships with the Killer AX1650 WiFi module which, at the time of this posting, is not supported at install for Ubuntu 16.04+. After banging my head against the wall and contemplating reinstalling Windows to check if there was a hardware issue with the WiFi module, I finally stumbled upon the answer here.

The XPS 7590 is a beautiful machine, so I hope this helps someone.

The accepted solution from here works for me except that Ubuntu does not come with the make command. As I had no Ethernet port and obviously no Wi-fi, I had to install build-essential which provides make offline.

So to install it I took it from Ubuntu ISO file, as build-essential is not installed but is available.

sudo mkdir /media/cdrom
sudo mount /home/bernard/Downloads/ubuntu-18.04.3-desktop-amd64.iso /media/cdrom
sudo apt-cdrom -d=/media/cdrom add -m
sudo apt update
sudo apt install build-essential

Don't forget to remove it after by commenting out the cdrom line in /etc/apt/sources.list.

If the driver is on a USB stick, you may run into permission issues while running make commands if you use filesystems that don't really support permissions.

Warning!

Check the kernel version before continue. If uname -r output is 5.0.0-38-generic, DO NOT install iwlwifi-backport driver on your machine as it leads to system freezes when Wi-Fi is turned on.

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The link in the accepted answer is dead so I'm pulling the referenced solution from Google cache and leaving it here for future seekers.

Killer AX1650 In Debian/Ubuntu 16.04+

Some users have expressed a desire to use the Killer AX1650 in Debian-based Linux. If your version of Linux does not support the Killer Wireless AX1650 at install, and you are using Ubuntu 16.04 or later, or another version of Debian Linux, you can use this guide to backport the drivers from the latest version of Ubuntu/Debian, enabling the Killer AX1650 in 16.04 or later. We have confirmed that this will result in wireless connectivity in Ubuntu 16.04 with the Killer Wireless AX1650.

If the device you are attempting to install WI-FI drivers on has NO Internet access at all, please refer to the following article

Please note that Secure Boot must be disabled in your BIOS before following these steps. If you are unsure how to disable Secure Boot, please refer to your machine or motherboard’s support materials or website.

Type or copy and paste the following commands in a terminal, one line at a time, pressing Enter after each command.

$ sudo apt-get install git
$ sudo apt-get install build-essential
$ git clone https://git.kernel.org/pub/scm/linux/kernel/git/iwlwifi/backport-iwlwifi.git
$ cd backport-iwlwifi
$ make defconfig-iwlwifi-public
$ make -j4
$ sudo make install

Additionally, you will need to ensure you have the latest iwlwifi firmware:

$ sudo git clone git://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git
$ cd linux-firmware
$ sudo cp iwlwifi-* /lib/firmware/

Then restart.

Once you have done this, you should be able to connect to your wireless access point.

How to disable Secure Boot? See Alienware Ubuntu Based Systems: Disable Secure Boot to Modify or Replace the bootloader