Mike Adams seemed to use a derogatory adjective saying something like "you have to find some ______person who will trade to you U.S. dollars for cryptos." Adams also seemed to indicate that such trades are separate from the blockchain environment. Jsnip4 has done a couple of videos on this and it seems one has to do such a trade very carefully following wise steps.
I don't know why anyone would want to exchange them for FRN's, silver dollars yes. Many places accept them for goods and services.
I and Madfranks and perhaps others on this forum have exchanged crypto currency directly for silver/gold.