As far as I know, the Chromebook is Linux Debian but it needs to be active in the settings, just like it shows on the official google website. But I've never had the opportunity to own a Chromebook yet.
Linux is disabled by default. You can activate it at any time in Settings. At the bottom right of the Chromebook, select the time. Select Settings, then Advanced, then Developers. Next to "Linux Developer Environment", select Enable. Follow the instructions on the screen. Setup can take 10 minutes or more. A terminal window appears. It has a Debian 10 (Buster) environment. You can run Linux commands, install more tools with the APT package manager and customize your shell.