Aymen Arfaoui strapped on a plastic Uber Eats bag and checked his cellphone for the fastest bicycle route before pedaling into the stream of cars circling the Place de la République. Time was money, and Arfaoui, a nervous 18-year-old migrant, needed cash.

"I'm doing this because I have to eat," he said, locking in a course that could save him a few minutes on his first delivery of the day. "It's better than stealing or begging on the street."

Arfaoui has no working papers, and he would pocket a little more than half that day's earnings. He said he owed