First of all, gratz for your game, really an awesome work.
Second and totally off topic, why publish here and not on any major platform like Steam / Epic ? Wouldn't the reach your game get compensate taxes ? Aspiring game dev here.
I thought of myself first, of course ;-)
I had forgotten that Railbound is a Unity game younger than 2015. The last Unity game I know that works on my system is made with Unity 5.1.
But there are probably other gamers who, like me, buy games exclusively at GOG; I buy games using Paysafacard, which is only possible at GOG.
I hadn't seen the game on GOG yet which is probably because I ignore Windows games that cost more than 10 Euros. The probability that Windows games will work for me is not very high and I don't want to give away too much money. I use MX-15 Debian Jessie 32 bit and Wine 1.6.2-20, sometimes Wine 1.8.1.
Not all people are Polish ;-)