This has been going on for as long as the dollar has been the dominant currency for pricing oil. There are a variety of structural reasons as well as pure inertia that mean this is a quixotic quest, even more so if you're the EU which doesn't have much power to do anything in oil markets given that they're dependent on it as a consumer and don't produce much.
https://business.financialpost.com/...ransactions-in-sanctioned-iran-sudan-and-cuba The EU (France and Germany - can't think of any other countries within the EU who get a say), have never forgiven the US.
Plenty of the producers are not happy either (e.g. Russia, Venezuela, Iran) but it would take a serious shift (like the US f*cking other countries over more than usual). Also, there is a common conspiracy theory (with some snippets of evidence) that any one country that wants to sell its oil for non-dollars gets democracy on the double.
The happy problem (From the U.S. perspective) is that those producers and the EU have disparate enough interests that it's difficult to get them to agree on what the alternative should be, even if they do all want an alternative. I'm sure Venezuela wants it to be their cryptocurrency "the petro"...wonder how that's going, come to think of it?
The alternative (if any) does not have to be a single currency, it can be a basket of currencies that include those of the major stakeholders but excludes the US dollar. It can be in the form of some cryptocurrency backed by the participating governments.