You can switch any chromebook into "developer mode". Then you get bash within the terminal app, with full sudo access.

At that point, as you poke around, you find that chrome os is actually built on top of gentoo Linux.

And there is a 3rd party pkg manager (chromebrew) which gives you gcc, and thus a whole host of additional pkgs.

Yup, its linux all right. Even without going the crouton (chrome into another distro) or crossing (vm running separate linux distro) route.