I think there is no such thing as alternative and unregulated paper money and only virtual currencies can be unregulated or decentralized. Any paper money or fiat that not issued by the government would be illegal and government will not even create any alternative money that beyond their control. In the older times, they used gold, silvers, porcelain and other goods in the barter trades because they have values even without government approval.
In bitcoin world, Alternate currencies are the "Altcoins" and not the Fiat. Fiat is already there and we are getting rid of Paper money in order to use digital currency which has much more benefits than the old paper notes.
right, in the world of cryptocurrency there are coins and altcoins, and to replace fiat currency into digital currency is not easy, although later I'm sure it will happen too. but maybe a generation after us