No HR person would allow unpaid intern positions in 2021. It's very clearly illegal in the United States.

When I mentor college students, the only times we hear about unpaid internships are:

1) Unfunded wannabe startups or small family businesses who don't understand what they need, but they assume they can convince some naive kid to do it for free. No one with actual skills or prospects takes these jobs. Job boards remove these posts if they're moderated.

2) Students who struggle to get a normal internship, so their dad/uncle/cousin/neighbor lets them do an unpaid "internship" off the books at their company to get something to put on their resume. They don't really do much work, but now they can put a line on their resume and claim some work experience for the next interview.