Banks in Germany started to allow people to buy and sell cryptocurrencies this January 2020. I think other countries will do the same soon, Japan might be another country with such services. In the beginning, someone has to start something so others can follow suit.
What are the other countries where anyone legally can buy/sell cryptos at commercial centralized banks?
Are you sure of what youre saying? The news I saw never said that any bank in Germany is buying and selling Bitcoin or any cryptocurrency, rather the news was that a new law was passed and according to the federal banks may be allowed to buy and sell cryptocurrency. And of course Im hoping to see them start doing that, but none of them have started doing because I checked if there was any bank that has already started selling and buying Bitcoin from their customers and there was none. Im looking forward to other countries doing the same.
Someone once said its going to be China, but I dont believe that. Any country with plans to release its own cryptocurrency wouldnt tell banks to be buying and selling Bitcoin, because they would want their own cryptocurrency to be the one issued out by the banks.