Thanks for this link. Have you done this yourself? How big of a challenge would this be to a tech novice? I ask because my kids have a couple of aging Chromebooks.
I've not done it myself but I've done a ton of other linux projects. Just read through the instructions and see if there is anything you don't understand. Figure out your exit strategy before you start: how do you revert to ChromeOS if you are at an impasse? Trust that there are at least dozens of people who have already run into every problem you could have and have posted about it somewhere on the internet with a solution.
Sounds like you're in a good spot to try it since you have more than one on-hand. Good luck!