Does this mean that the digital equivalent of cash in the form of an appropriate cryptocurrency is officially also mandated by law?
Doesn't matter how you turn it, cryptocurrency is never replacing cash. Digital currency, maybe, but I would always take cash for any inperson transaction.
The better way to consider: There are arguably favorable properties that ARE in cash, that are NOT in mainstream bank-led digital payments, and that ARE in cryptocurrency. Some people have already discovered this and use it for these purposes. Now, it is also true that the cryptocurrency space is a breeding ground for scammy behavior.
The only question is -- to what extent might cryptocurrency get more popular for "legit" purposes.
Like for many things before, gaming is likely to lead the path for more adoption, the tokenomy has been a thing for many years there now and crypto nicely provides the infrastructure for building a token system on that already. networks with low fees are there and smart contracts can even be written in JavaScript, with companies providing transaction gateways etc etc etc.
At this point anyone doubting crypto has continuously be gaining legit adoption must be blind or in denial.
Developer tooling and ecosystem getting better and better, the whole crypto crashes aren't putting a dent to that.
All it takes is more absurdity from a government for a spike in adoption. See Argentina and Nigeria.
It is already popular for legit purposes, except that the news rarely report it, it makes better title to say some group is laundering crime money using Bitcoin.
Note that the "debt" part is important. You can refuse to take cash for a new transaction, but not one where the other party already owes you money.
I believe there have even been court cases that held that the type of restaurant that requires you to pay before getting your food can refuse to take cash, while the type of restaurant that lets you pay after you've eaten cannot (because that makes it a debt you owe). Don't quote me on that, though.