I've read through old discussions on this topic. Not everyone has a last name at birth, so "Unknown" is not a good option. But you have to put something. Native American project says that the name of the tribe should be used. That feels wrong and even a little creepy for those who lived in the 1800s or earlier. Like Geronimo, Sacajawea, Pocahontas and so on. But when it comes to someone who lived recently, whose parents are still living even, it is utterly and completely wrong. IMO.
I knew Lah-huh-bate-soot for his entire life. It was completely and entirely intentional that he came without any last name; only a traditional name, handed down through the family. I personally had some hassles trying to make a plane reservation for him when he was a little tyke. I don't see why we have to force a name onto him which his family never intended, and which never was his name. His birth was recorded with the tribe, and that was his legal name.
Please: May we have "None" as an LNAB option? Rather than imposing something that doesn't fit? That will never fit? We supposedly put priority on using the name as given at birth. Why are we forced to employ the disrespect that goes with imposing a name that never ever ever was his?