There is the People of Color community. beehaw.org/c/poc There have been indigenous related topics posted there. My personal 0.02, being Native myself, is that there would really have to be a critical mass of Native people on here for a specific group here to be worth it imo, and the PoC community is pretty slow as is post-wise. If it was overflowing with Native content drowning out everyone else, it would be more needed.