1) nothing that's happening right now would be possible if such a separation were axiomatic to the general population, which is why all of the states involved work so hard to infuse these ideas together into a single, inseparable concept of nation-state. the states of the world want you to believe that you are a member of a nationality, and that that nationality defines who you are as an individual. a mere moment's reflection realizes the contradiction in the idea that individuality is defined by collective identity, but that kind of clarity of thought is very effectively repressed. it is only when you identify as a member of the collective that you can be manipulated into behaving the way people are behaving in ukraine.
2) the ethnos does not exist. the science is now clear on the point that any random sample of self-identifying ethnic russians is going to contain backgrounds from pretty much everywhere in the world. you can identify mutations, but they make up fractions of the population. the fact that russians and ukrainians are ethnically indistinguishable does not imply that ukrainians should not have local governance. an educated populace would go beyond the point of rejecting a tyranny of the majority to acknowledging that the majority is itself actually a fabrication and move beyond. i'd like to be optimistic about that, i would like to declare nationalism dead, but i don't have any good ideas about getting there.
so, you have these two things in contradiction to each other: the nationalism that the state enforces as a means of ownership and the biology that discards it as nonsense. as is so often the case, this is a battle between information and authority.
but, the sooner that we collectively realize that the ethnos is a myth means the sooner that we break free from statist control, and avoid the particularly profound idiocy of ethnic violence between genetically indistinguishable people - be it in ukraine or in palestine or in ireland.