Where does Ukraine-Poland "apple of discord" come from

The recent Ukrainian-Polish disputes should be considered in a broader context: today, centrifugal processes and those of archaization are taking place not only in Ukraine or Poland, but also in the entire West. That is why the Trump and Le Pen phenomena have arisen. That is, a nationalist card is being played across Europe because a liberal democratic project has shown that it does not meet the wishes of the general population, especially its active part, so returning to nationalism is a more natural process for these countries. However, nationalism is always about history, not a future. It’s not a European project, which is based on absolutely new principles.