Oh, derp on me. It stated plainly in the "Choose a candidate" area that I can not choose a person who is already an Account Holder.

Still broken in iOS 16.1 (2022-10-28). I have an iPhone 11 that refuses to use the proxy (tried forgetting wifi, after a cold restart I could connect). But I have other test devices where the proxy works fine on iOS 16. @eskimo As in, you enter proxy information, even a random invalid address/port, and when you access the network, all data comes thru uninterrupted. As if the proxy setting does not exist or is ignored entirely.