These restaurants should be called "social media restaurants", they exist for the purpose of social media, they serve social media, they are critiqued by the social media and many last as long as social media posts do and are great fodder for social media in general.
"underground restaurants" are they akin to rebels of the "Arab Spring" or are they business' that are not registered, don't have health certification, and don't pay taxes that makes them revolutionaries? Or just social media restaurants.
I am going to have an hamburger now at Billy's drive in.