I guess, given that this is inserted into the preamble to provide a context of what happened in the past, I don't know that we need to try to define who the populations are or exclude other people.
I think that generally in the preamble—and maybe this is something that the team could respond to as well—I've been trying to make it so that it's a general acknowledgement of what happened in the past: that indigenous peoples did thrive before settlers and other groups arrived and forced colonial policies to be implemented.
I don't know that we can have a specific word to try to define it. Maybe this is something that the team can try to respond to.