I’d also look at how Herodotus using the word (even making it into a verb, once). The consent status of such relationships, as with bride-snatching in the Caucasus, is not possible to generalize about. And Sally Hemmings’ relationship with Randolph Jefferson (likely) or Thomas Jefferson (rather less likely) is hard to say a lot about. What would they have said if you could ask them about it? Unknowable, I think. But unlike the Homeric society, there was no social approval of the (common) practice in the American South, and the cases of the relationships (or at least the offspring) becoming regularized were extremely rare, as far as I know. [Still, I can’t recommend enough a careful read of the Slave Narratives collection at the Library of Congress for anyone interested. I recall a number of frank discussions about personal feelings about this sort of thing.]
Anyway, as usual, maybe a better model than the American South would be the North African slave trade, where the concubinage of the often white Christian slaves had a recognized place in the society, possibly one that traced back to an earlier period. But that was a far more complex and advanced place and time than the Homeric. Maybe a still better model for the Homeric Greek concubinage could be in tribal slavery practices, either in Africa or among American Indians? In the last at least, captured “concubines” could often be fully legitimized fairly quickly.