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Merriam Webster - Indigenous: of or relating to the earliest known inhabitants of a place and especially of a place that was colonized by a now-dominant group

Wikipedia - Indigenous peoples are culturally distinct ethnic groups whose members are directly descended from the earliest known inhabitants of a particular geographic region and, to some extent, maintain the language and culture of those original peoples

By what measure are Maori not indigenous to NZ? If another group arrived first, they certainly didn't stay, and even by your own measure of "time of inhabitation", Maori have been here the longest (at least 350 years before Europeans).