Well, for starters, with dm-verity and secure boot to prevent modifications to the root filesystem. IMO it's beside the point. Calling ChromeOS "Linux" is like

Well, for starters, with dm-verity and secure boot to prevent modifications to the root filesystem. IMO it's beside the point. Calling ChromeOS "Linux" is like calling cells "mitochondria". One could argue that the same could be said about the somewhat standard Linux desktop stack you'd find on Ubuntu or Fedora installs, and that's true. However, that's probably mostly just a consequence of the fact that Linux doesn't have an actual standard userspace. The closest it has is the defacto set of components you're likely to find in any GNU/Linux distro, and they are quite different than what you'll find when you boot up ChromeOS or Android.