The areas in question were Russian for hundreds of years, which is why they are ethically and linguistically Russian today.
You don’t want to play this game. Many areas of Russia itself were not majority ethnic Russian historically. I’ll buy you a clue. Putin won’t be transferring “administrative duties” to the locals in those areas.
I don’t need your clue. I make no argument that the territorial borders of Russia are inviolable nor I do claim that Putin would be willing to let,say, Chechnya go, even though Russia would be far better off without it. What I do say is that if a region that has been made subject to one governmental unit prefers to be subject to another, they should be allowed to switch. I am certainly not willing to be taxed or to see Americans killed for the purpose of keeping Slaviansk, for example, subject to the government in Kiev that was installed by a coup.