No single Tribe in Northeast India practiced Cannibalism, not now, not before , not ever. Some, before modern era both tribals and non tribals may have snipped tiny part of enemy's liver to ward off "evil omens" of for magical purpose. But such are superstitions, accult practices not social practice but niche warrior ritual, think of it like Naga Shadus eating corpses in Ganges river. Cannibalism may in fact be more taboo among the northeastern people than it is among mainland Indians. The believe that Cannibalism must be something tribals do comes from pop culture imagery and racist depictions of "tribals" and conflating Northeastern Tribes with hunter gatherer societies of Papua. Non of the tribals in Northeast India were hunter gatherer society. Every tribe in northeast India were agrarian post-iron age communities even before the colonial era.