There are quite a lot of Ukrainian-speaking users on the forum, there is not enough general topic for discussion of issues, it is not active precisely because it is inconvenient to search for information there due to the fact that it is fast flowing. The demand for a separate thread has existed for a long time, and there are enough reasons for its creation.
I don't think it's make sense to say the thread is not active because of fast flowing, what about the Nigerian when they also start with one thread and then @theymos create a local board for them since they're have a good amount of traffic.
I can't read your language and Russian language, but my assumption you guys are more active in Russian board, correct?
That's make @theymos think no need to create Ukrainian board because Russian board is already enough.
As Jawhead999 had mentioned, there's every possibility for Theymos to take into account the next set of locale to get their own local given a board, but before this, the Ukrainian thread has to be very active, mebers needed to post there and increase the activities on the locale thread, one of the criterials taken into consideration is to check on their activities and how active the members are, the numbers of influential members amidst them of reputable character and good asset to the forum, it may take a while before such request could be attended to, because who knows maybe they were under surveillance as part of their assessment before such request could be granted or not.