So there really is no legal role for these? Not only are they not G83, but wiring regulations also prohibit connecting any generating device using removable cabling. There is simply no situation I can find in which it is legal to operate such a device. Hobbyists just get away with it because the grid operator isn't going to notice.
I was hoping there would be some sort of exception for micro-scale, maybe <1KW, but... nope. Not that I've been able to find.