I'm not anti-crypto, but I honestly don't know what you mean by "sound money". Could you elaborate?
* https://fee.org/articles/what-do-we-mean-by-sound-money/
* https://mises.org/library/principle-sound-money
* https://www.aier.org/pertinent_category/sound-money-project/
But I think it's relevant to split hairs a bit and say that "sound" often has the sense of "firm" or "solid/reliable", but that is not an inherent property of non-governmental currencies that can be controlled by groups that are no more beholden to users of the currency than governments. (Consider Facebook's attempt at creating a currency as an example)