More clues... Found this picture at https://www.dhmlsr.tk/ProductDetail....37124&pr=66.88 The site looks a little sketchy to me so go at your own risk. I included the picture here, not much if any more info on the site other than that they appear to be offering the trailers for sale for $66.88. This is the only picture and there is no real description.

It looks to me as if they are using a nutted axle and a special very deep nut design that you pins click into. There are a number of ways you could rig up something to make that work.depending on the bike and what you are willing to do.If the special nuts are not available (likely) you or someone with a lathe could make something for you. You'd need to go to a nutted type axle for that solution. I could imaging this working easily with a thru axle bike with some custom parts (along skewer bolt and some spacers.