Sorry man, but it's not about language affinity. It's about visas and work permits. It was much easier to get work permit in Russia than in EU for Ukrainians and it still does. But last two years things started to change, Poland gave about 1 million work permits to Ukrainians in 2015. So, no pain
Then more power to you. The Polish board is already available, so, I assume, you can safely start posting there, all the while the Ukrainian board is not a priority. That would be quite logical, since Ukrainian is closer to Polish than to Russian, right? You might even want to substitute Roman letters for Cyrillic script to get even closer than that...
Personally, I would be happy to see you and your buddy posting in that board