I know that you can't invite people over to claim Amiibo campers, but can you give away non-Amiibo campers in your campsite by having a friend/guest talk to them?
Hm, I don't know for sure but I have seen people auctioning off their villager once they have packed their boxes. In order for your friend to come get the villager, the villager has to come up to you and ask if they should leave. If you say yes, then the next day that villager will have just a bunch of boxes in their house, and I think that's the point where you can invite a friend to come pick them up (granted, your friend has to have an empty plot on their island)