I can't say anything about the GUI interface in the video and haven't run a full blown Desktop like this myself. I just grabbed the first video I found on Google. But yes, I'm running Linux locally on a Pixel phone since the Beta. Like I said bellow, it's still at early stages for Devs to work in, but it works. And before that we already had Termux:X11, Andronix and several other solutions on different stages if maturity.

Here's a more reliable source running Doom several months ago (I haven't done it myself either): https://www.androidauthority.com/android-16-linux-terminal-doom-3521804/

My honest opinion is, even if the video in question is bogus, it's just a mater of time until what we have surpasses what it's being shown there.