My country made this quite easy to be fair. Paypal is banned in Turkey, so you can't buy it that way, but it is allowed to put your money into Binance or any other local places like Paribu etc easily. Meaning that you just wire your money there, and it gets there, so the exchange account gets credited with that much fiat that you sent, and then you can buy whatever you want. For all the nations that have trouble with payment services, I suggest exchanges that directly deals with it, and if there is none that exists today, then it is quite clear that you could definitely make that work and make one yourself.