Most or all of Ukraine was part of Poland (or Crimean Khanate/Ottoman Empire), then was added section by section to the Russian Empire. Never had an independent existence at all, except during brief and unsuccessful rebellions. This is as opposed to Poland, which had something like 7 centuries of independent existence as a state when it was finally partitioned.
That disappearance, BTW, took place in 1795, and Poland reappeared in 1918. So 123 years, which isn't exactly two centuries.
You are correct, however, about the very concept of nationalism. It didn't take root, at least in central and eastern Europe, till the 19th century. So talking about conflicts between the Russian, Polish and Ukrainian "nations" in earlier centuries is at best anachronistic.
Multiple "republics" existed in Ukraine for varying lengths of time between 1917 and 1919. None were ever stable or organized enough to really be considered independent by any logical standard.
At one time, the Polish-Lithuanian Commonwealth was the largest Kingdom in Europe.