Cryptocurrencies in general are a good alternative. They're strictly unsanctionable and, depending on the currency selected, also untraceable, so secondary sanctions would be extremely difficult to apply with any kind of granularity. National-scale sanctions, evidently, would still be quite feasible.

Alas, that kind of anonymity runs counter to the very soul of the European bureaucratic ethos. They absolutely want to know in detail where every single cent goes, plus the power to block transactions at will, so they're looking into some magic solution that allows them full purview and full control while perfectly denying the US and its spy apparatus the possibility to also see into it, an impossible combination of requirements.

And I say all that as a fan of the EU. It's one of their many blind spots they need to overcome if they ever want to become a technological superpower.