Linux
This used to need a lot of documentation. Now it needs a few clicks.
Google official guide: https://support.google.com/chromebook/answer/9145439?hl=en-GB
The key steps are:
Enable Linux Support (Extract from the Google docs)
On your Chromebook, at the bottom right, select the time.
Select Settings ⚙ and then Advanced and then Developers.
Next to ‘Linux development environment’, select Turn on.
Follow the on-screen instructions. Setup can take 10 minutes or more.
A terminal window opens. You have a Debian 10 (Buster) environment. You can run Linux commands, install more tools using the APT package manager and customise your shell.