There are two good uses for these people, and I'm okay with giving them the choice: forced labor to help the infrastructure of the country, being given a reasonable section of land that they can call their own, heavily fortified and walled off. That can include trash pickup, working on our highways, anywhere we could use a few million bodies to help the country overall.
Or they could become Soylent Green, potentially be mixed in with fertilizer, or to be useful to the medical experts to help us avoid another pandemic with some cutting edge treatments and experiments.
I can't really think of anything else that they're good for. So I say we give them a choice. They won't like the other options.