Not sure why this page says Ubuntu won't work. MrChromebox's firmware just turned it into a regular UEFI computer. I've had Ubuntu Mate 22.04 working on a Chromebook just fine.
Mint and Ubuntu LTS ship with a 5.x kernel at the moment, so that may be the problem. Normal Ubuntu is updated enough to work, but many people will probably prefer the LTS release lest they need to update every 9 months.