Can you “legally” put it down? Yes. Will a college consider it without tribal membership? Depends. And AFAIK, there is not comprehensive list of what colleges will consider it without a tribal membership number.
That said, there is no check box on the application that says “Check here if you are URM.” You list your race/ethnicity (if you choose) and the college will use that info as it sees fit. Each college, where not prohibited by law, will decide what is URM and also decide how much of a bump, if any, this will give an application.