To overcome the ongoing sanction people find the usage of cryptocurrency a way, but the same can't be used by the government which will destroy the money value of ruble. There is not much of value destruction with ruble and the recent plans of Putin to receive payments in Rubles for oil and gas will once again boost the value. Very few cryptocurrency exchange have given access for the Russian residents. Russia is looking for a source to overcome the ongoing situation and it doesn't look like a long term plan.
As for payments in roubles, they made export companies to sell 80% of foreign currency got with export revenue before plans on selling anything for roubles. So the difference between 80% and 100% is not so big. Yes, it helps with the rouble rates but it is far from market situation.
Main problem for government for bypassing sanctions with crypto is not only that it can destroy the money value of rouble, it can be hardly done as Russia is a big country with a huge import volume. Even if it can get enough crypto for trading (which is hard by itself as all amount of crypto holded by Russians is just about 100-130 billions of USD
according prime minister Mishustin) it is impossible to import such volumes of goods into the country unnoticed.