I know history. I know that Ukrainian resistance to Soviet reconquer lasted almost a decade after WWII. And that was with no help from outside. Even if Russia does “win” they’ll be getting attacked in that territory for a long long time.
I do not believe Russia will conquer but they will attempt to steal as much land as possible. The Cossacks will still ride the Steppe and the wheel of history will turn again in the future. The eastern Ukraine is very much the soul of the Ukraine. Even my Russian-speaking Donbas family say so. In the Russian-speaking areas, Ukrainian is still spoken in many villages.