They do. As for non-Ukrainians, as long as it's not Russians, they're generally pretty hospitable to everybody.
As for the conflict with Nichan, the main reason is in both boards' origin. Before either, there was Uchan. It was quite big for the time and definitely larger than everything that followed. Due to it's size it began manifesting the problems all big boards have. Toxicity, low effort shitposts etc, you name it. That's when Nichan's admin, Deimos decided to secede, creating Nichan. Main reasons were to create a less toxic community for comfy talks. Unfortunately, it died in 2013 though. Then, various boards came and went as "something that will replace Uchan". During all that, Uchan actually went down. In september of 2016 it suddenly stopped working. As it turned out, the admin of Uchan died a few months ago, so his site actually outlived him. After the death of Uchan refugees started to flood the remaining boards. One of the boards that got this wave of new people was Kropyvach(though way less than Fainach, that was the biggest for around a year or a half). In 2017-2018 it became clear that Kropyvach is becoming the biggest Ukrainian board out there. In 2020 Nichan was suddenly revived. People who weren't satisfied with Kropyvach came here. And most importantly, the ideas behind Nichan and Kropyva are somewhat different. Kropyvach is more of an average imageboard with all the edge and toxicity involved, while Nichan is more about idle politics and edge free chatting.
Kropyva = Ukrainian 4chan
Nichan = Ukrainian 8chan