My two cents. If anything, I should India (maybe I can't talk about the rest of the countries as I may not know them as well as I know India) try it make it as legal as possible. Maybe, they may not be able to make it legal tender or an equivalent to currency, but banning them is not of going to be any big benefit to the government for the following reasons.
Indian people, to quite some extent have seen or understood how beneficial it could be in terms of technology and also, as a short term practise for trade and the financial benefits of it. So it is going to be very difficult to get this banned as they will only look to circumvent the banning.
Almost like a year ago or something, Indian Govt had banned porn websites and we all know how it went. So, banning cryptocurrency or any efforts towards it is just going to yield the same results.
By making regulations to the crypto market or it's exchanges, (though I know it is easier said than done) the government can make best use of it. If they try to ban the use or trade of it while the other major countries don't, it will be very easy for people to start trading them on exchanges outside of India and may pave way for more Hawala than ever before.
It's time that the government had indeed understood, just like how efforts to complete prohibition to liquor made it easy for illicit arrack and it's pandemic effects messed up the well-being, banning of crypto currency could well be the beginning of another aftermath like liquor prohibition.