Yeah, there’s a long and bitter history of the descendants of those slaves getting tribal membership.

In very recent good news, the Muskogee freedmen just won their tribal memberships as well. IIRC, the Muskogee freedmen still have some unique dialects - me and a buddy threw around the idea of doing some documentation/research on it back in college.

Native American slavery wasn’t always the same sort of chattel slavery practiced by white Americans - intermarriage was a bit more common and the boundaries were often (if not always) fuzzier.