I have a HP Chromebook G4 from 2014 that won't receive official Linux (Crostini) support, so I decided to use Crouton to install Ubuntu instead.
I thought some of you might be interested in this, so this article presents step by step instructions for installing Ubuntu on any Chrombook model, using Crouton. There are also a few tweaks / tips, and instructions for removing it.
Crouton, or Chromium OS Universal Chroot Environment, makes it easy to install Ubuntu or Debian in a chroot environment on Chromebooks, no matter the Chromebook model or architecture. Using Crouton, you continue to use Chrome OS, but you can easily switch between Ubuntu and Chrome OS when needed.
Compared to the Crostini solution for Chrome OS offered by Google, Crouton has wider device compatibility, and it enables direct hardware access. Also, compared to virtualization, Crouton has zero speed penalty since it runs natively.
On the other hand, Crostini is an official project and doesn't need enabling developer mode (which is required to be able to install Ubuntu or Debian on a Chromebook using Crouton). Since your Chromebook runs in verified mode, it also means Crostini is more secure.