Can you? I've got to imagine that transacting in a runaway inflationary currency is going to get you bad rates no matter what.
If you want to buy crypto using rubles, Lebanese pounds, Venezuelan bolivars or anything else, you need a counterparty who will accept that currency as payment. And if your currency is losing a lot of its value every day, with no end in sight, your counterparty will not give you anything approximating the official exchange rate, even on an open market, because accepting payment in that currency immediately exposes them to that currency's inflation.
If you want to buy crypto using rubles, Lebanese pounds, Venezuelan bolivars or anything else, you need a counterparty who will accept that currency as payment. And if your currency is losing a lot of its value every day, with no end in sight, your counterparty will not give you anything approximating the official exchange rate, even on an open market, because accepting payment in that currency immediately exposes them to that currency's inflation.