Seems like to me that it should be fairly easy to separate the real Ukrainians from the africans and middle easterners.
Over a week ago there were reports that in the second largest Ukraine city, Kharkov (old Russian map spelling), to the east, there were 300,000 students trying to go home. That city has more than a score of colleges and universities. A number of these students were African, Middle Eastern, etc. and having trouble getting home or across borders. There may be some confusion here as to who is a student and who is a foreign refugee, etc.