Given the ample reporting of Russian speakers in places like Odesa switching to speaking in Ukrainian as a result of the 2022 invasion to distance themselves from Russia, or the difficulty the Russian occupiers of Ukraine has had in finding people willing to work for them, or the fact that the current president of Ukraine is himself a
Russian-speaking Ukrainian, or the fact that in the 1991 referendum, a majority of people in every Ukrainian oblast (
including Crimea!) supported being a part of Ukraine rather than Russia, I don't think it's that hard to say what the general appetite of Russian-speaking Ukrainians becoming part of Russia is.
Or, to use an analogy with a different language, Putin's argument is akin to saying that a majority of Irishman want to be a part of England, because they speak English.
Don't confuse language for cultural identity.
(And, FWIW, I have fallen for this propaganda in the past; I've just been successfully educated since then as to why the simplistic linguistic map is fundamentally the wrong way to look at the conflict.)