If Native Americans in any significant number are receiving UBI already, then that's news to me. They're disproportionately in poverty - and thus disproportionately eligible for various strings-attached welfare programs like food stamps - and tribal members / reservation residents receive some additional pittances of federal funding as a sort of "sorry we stole your lands and attempted to genocide y'all, now shut up about it and take this spare change we're throwing at you", but that's about it. The only thing even vaguely resembling tribal UBI of which I'm aware is annuities from casinos, and last I checked those don't come anywhere close to even meeting the poverty line, let alone sufficient for anyone to live off them - i.e. they don't satisfy the "basic" in "universal basic income".
UBI is the solution, not the problem - and on the topic of Native Americans, funding it can and should start by taxing the unimproved value of the very lands we conquered from them.
