The reaction on the Nintendo Switch Hacking subreddit is characterized by both excitement and skepticism. 

One skeptical user says:

Alright f0f...youve peaked our (Edit: my) interests. But is this dual-boot, a complete install of Linux, or total bs and you've got a Pi or Rockboard in there. A teardown of your machine while it's running would prove all...

But another commentator pointed out:

It's really not hard to believe someone got it running Linux at this point when Nvidia has Tegra X1 Linux images on their site.

I'm thinking this is totally legit.