Ukraine has over 8 million ethnic Russians while the rest of the named countries have >100,000 Russians each. Poland has around 10,000 only.
Is their any reason why Poland doesn't have a sizable Russian minority, considering it was once a Soviet satellite state and considering it's close proximity to Russia?
After WWII Poland was literally moved 200 miles West by the Soviets, so that Belarus became a Soviet SSR instead of Polands Eastern borderland. So the vast majority of Russian speakers in Poland were simply annexed by Stalin. The Poles were given the former German territories of East Prussia (except Kaliningrad), Pomerania, and Silesia in return. And plus the Soviets forcibly moved ethnic minorities East while moving Russians into those vacated territories. A significant portion of Ukrainians attempted to side with the Nazi's, until the Nazi's turned on them, so the Soviets remembered and resented that. Many got to colonize Kazakhistan or mine gold for Uncle Joe.
Poland was a Soviet satellite state but it was not part of the USSR, unlike the other examples you've mentioned. This meant that there were restrictions on Russians moving to Poland.