They could build housing on federal land, or lease the land to housing developers under favorable terms. I don’t believe the federal government can be bound to local zoning laws.
Now that wouldn’t help you in a city like Boston or New York, but there are plenty of states where the federal government owns the majority of the land.
That’s true, they also can circumvent restrictions.
But give the historical relationship between the government and the Native American organizations, I can’t imagine most tribes would politically get behind using their limited reservation land to house people from outside the tribe.
That's a good point. Still if the agreement is to lease to people oppressed by the US government they may agree to it. IIRC racism etc in housing is not illegal on an Indian Reservation so they might agree to certain classes of people they commiserate with if enough cash is in it for them.
Now that wouldn’t help you in a city like Boston or New York, but there are plenty of states where the federal government owns the majority of the land.
https://ballotpedia.org/Federal_land_ownership_by_state