Some people think of "alternative currencies" as wonderful solutions to economic problems. But obviously, no currency can have any significant impact without becoming legal tender.
So what would happen if a country actually adopted an "alternative currency" as legal tender? Well, unless you're in El Salvador, you're in luck: it's already been tried.
December 2021 Update
There's even better news (that is, unless you still haven't fled El Salvador). If you were waiting for the occasion to test your great idea of building a city next to a volcano, someone else might do the job for you.
February 2025 Update
After El Salvador's conservative President asked his party to walk back, there's now a clear answer: the country would be forced to drop it, in this case to keep borrowing from the IMF.😅