OpenSSH, Tinc, Wireguard and a myriad of other open source tools can also be used as a VPN. One only need a place to connect to and egress from. To me that means VPS/Server providers will also need to do age verification. Most VPS/Server providers also allow configuring reverse DNS. That leaves only CIDR blocks as a way to tell it is not residential. One could also egress from residential elsewhere assuming the friend has spare bandwidth that could be balanced and capped using sch_cake.