I agree it should. German is like that too. I think it hasn't been reported yet. Looks like the nominative plural of the noun. so you could drop "the" or keep it.
Yep, it should be accepted. Not only because one might drop or keep it talking about the citizens of Ukraine; also because Ukrainian does not have articles, so "The Ukrainians" referring to some group of people translates to "українці" as well. Added it, now it's accepted. Thanks!