Gabe posted a great article on how to replace the built in Debian container on Chromebooks (Crostini) with Ubuntu in his article on Chromeunboxed here.
Its important to note that Crostini is designed to allow almost any operating systems to run in it. But the OS running inside needs to be able to communicate with the host OS to allow the two to interact well and work together. Gabe shows how to setup the OS in the container and then add the much needed ChromeOS integration packages on Ubuntu to do this.
You can find all ChromeOS devices which support Crostini here.