There is a split between Utah County and Salt Lake City. Though according to a friend (I moved away a decade ago) the "Silicon Slopes" locally refers mostly to the area in between (centered around north Lehi where Adobe's building is). However there's always https://en.wikipedia.org/wiki/Silicon_Slopes -- while the region spans SLC and Provo, the claim by 'tntn that the marketing purpose of "Silicon Slopes" was largely to concentrate on the more rural areas in between (i.e. most of Utah County) doesn't seem that unreasonable.

To clarify, I started this trend of listing companies, and failed to recognize that apparently "Silicon Slopes" refers to larger region than Utah County. Before looking into it more, I would have said that it was only Utah County, since there are massive billboards on I-15 southbound around Draper that say "you are now entering silicon slopes" and the phrase was coined by the founder of Domo.

My mistake. Since the edit window on my original post closed, I tried to explain in subsequent comments what I had in my head when making that first list so that people would realize they don't need to explain to me that all of Utah is not like MLMs.