Never. For Russia, that is a red line.
I think a Finland type arrangement might be a workable solution. Finland is a member of the EU but has also pursued a pro-Russia policy out of necessity, both during the Cold War and afterwards.
Ukraine should pursue a similar policy. There is no reason why being in the EU should be incompatible with continued closeness to Russia.
The EU should amend its rules to allow Ukraine to also join the Eurasian Union at a later date if it wants. Europe must not exclude Russia’s interests and make it a zero sum competition about exclusive trading blocs membership.
Finland will never join NATO. The principled approach of Ukraine should be the same stance - we want to be in Europe but we will never side against Russia.
Within that framework, a political settlement is possible. I think it will have to wait until Ukraine gets a freely elected government that has the legitimacy to speak for the country as Russia will never deal with its present leadership.
Want to end this? Two words.
President Cruz.