It's the compositor used on the Steam Deck.

I guess it was meant as a joke.

if you'd develop an embedded OS e.g. for cars, why would you use X11 in this day and age?

I would expect them to invent some janky custom thing running on fbdev.

Not sure whether you are aware, but car manufacturers were one of the earliest adapters of Wayland for embedded use cases.

Many servers have guis.