Actually, I was reading today that, due to the sanctions, Russia cannot access payments in euros that it receives. The article was in Dutch (
link), but it's based on this study:
https://www.bruegel.org/2022/04/a-sanctions-counter-measure-gas-payments-to-russia-in-rubles/
In short, the Target 2 system ("the euro area’s settlement system") is required to convert euros to rubles, but Russia can't use it cause it's covered by the sanctions. So that 'clever' approach in which euro payments are made to the European branch of the Gazprom Bank and then converted to rubles doesn't actually work. That's why Putin is demanding to be paid directly in rubles, and why it's important that countries continue to refuse doing so.
To be fair though: the Dutch article adds that it's not clear whether this blockade through Target 2 was intentional or a happy by-product. And it also says that those euros are not completely useless to Russia, as apparently they can use euros as collateral when dealing with countries that haven't sanctioned Russia (like China). That's complicated and costly though; a lot of money is lost on the way.
Anyway, I thought that was interesting.