It's a good question! In general, characters based on real people but in an entirely fictional setting/heavily fictionalized universe should be okay (Leonardo da Vinci from Assassin's Creed is a good example for the former, while Blackbeard from Our Flag Means Death is a good example of the latter). Characters from a loosely fictional or dramatized representation of real events, on the other hand, would not be accepted (anyone from the book/musical/movie Hamilton). This might just have to be a case-by-case basis thing, but I hope this helps clarify my thought processes on the matter a little bit!