There are news stories and videos about this happening, and the Utah citizens have set a petition against it, but I don’t know if that is having any effect, or if that it is even possible to stop this , since apparently the Utah politicians are in favor of it. You can see in this video where the security guard stops the reporter from asking questions or taking pictures, even putting her hand in front of the camera, and this is just at the front door of the compound . I know that there have been reports recently of people seeing the white UN vehicles in different places in the United States, but this is the first I have heard about the UN having an actual compound and declaring a part of this country to be “international”, and not under our government in this country.
From what I find online, this was a UN Conference at the Salt Palace Convention Center in SLC, back in August. The convention center has a calendar of upcoming events so I must assume that the "UN compound" was of a temporary nature. It did cost the SLC taxpayers about $700k, however.