Ask HN: What can we do as software devs to help cities absorb the new migrants?

That's not really a software problem.

Refuse to localize interfaces so that people around the world are forced to learn English as much as they were in the '90s. (That's how I learned it. :p)

Vote for a government that wants to limit immigration to what can be sensibly "absorbed" and enforce immigration law.

Help them move to other localities where there is housing and work for them. Perhaps create a job board of more rural opportunities. Make them aware that yes, they can apply for work permits.