It seems like there's no questions about unlocking iPhones here so forgive me if this is counted as off-topic.
I recently received an iPhone 7 from a friend that is locked to Sprint's network through what I think is a US Reseller policy which is a special kind of SIM lock that isn't done through a carrier but by the phone itself. I've been trying to find ways around unlocking the phone - it's near impossible. One route I've considered is purchasing an unlocking chip that some people sell (I'm not going to provide a link because I'm not sure that they're not a scam, that's part of what I'm trying to understand).
My question is how do unlocking chips work?