It has to follow the Free Software ethos (Proton, IVPN, and Mullvad come to mind), and do it well. I know nostr:nprofile1qy2hwumn8ghj7ct4w35zumn0wd68yvfwvdhk6qg0waehxw309ahxjup3xuhxxmmdqqsdngef474mycag4usksw8tghslqnxrqqrsg3jfglztjplphm6cp4c7auuy5 and myself had done this in the past, though he's done it for at least 8 years, if not 9 at this point.