Comes preinstalled with your choice of Ubuntu LTS 16.04.1 or 16.10 (officially), unofficially it seems they are tolerant of those who prefer other distros. A high-spec machine, solidly-built, which certainly cannot be described as “anorexic”. And with a price tag to match.

And unfashionably expandable, too:

In total, this laptop offers an Ethernet port, an SD card slot, 2 Mini DisplayPorts, an HDMI port, 2 USB 3.1 Type-C ports, 3 USB 3.0 Type-A ports, and both headphone and mic jacks. The GTX 1070 models even include a headphone amplifier.

http://arstechnica.com/gadgets/2016/11/system76-oryx-pro-review-linux-in-a-laptop-has-never-been-better/