It’s a Bike Shuttle Trailer. This one in particular seems to be the smallest one I’ve seen so far. I have a tiny car so I don’t wanna be hauling a refurbished lawn care uhaul trailer. I want something that can carry 6 bikes and a toolbox just in case.
You can buy trailer hitch racks that’ll hold 7 bikes, if you don’t want to build+pull a trailer.
(this one’s 6, but I saw one in person just the other day with 7 on it)
I actually had a mule something or other on my car. I left the bike attachment part at my parents in California. But maybe that’s the easiest thing. The harbor freight trailer idea looks pretty good too.