Reddit mentions of Thule Internal Hub Hitch Adapter - Shimano

Sure, the Decathlon and Yosemite are very similar, both have 24v 250w motors and 7ah battery which is a modest size but should get you 20km. They would be adequate for towing a trailer on flat ground and up slight hills. The Monark and GreatWhite use more powerful 36v motors suitable for towing a trailer up moderate hills. The Monark has a much larger 11ah battery than the others so you could ride further, plus it has a 3-speed internal gear hub that lets you shift up or down gear when you are stationary which is very useful in stop and go city traffic. The GreatWhite is good value despite having a smaller 8ah battery I like it has a front disk brake which should provide Good stopping power. The Trinx is a pedal bicycle weighing 6kg lighter so will be easier to carry onto a bus. Finally you must consider what service level you need, Monark (3 year guaranty) and Decathlon (2 year guaranty) will honor their warranty, you can take the bike into one of their stores for service, vs the other cheaper bikes you will need to research how reliable the shop selling the bike is providing after sales service.

To attach the trailer to the Monark because it has an internal gear hub you would need to add a Thule axle adapter like this https://www.amazon.com/Thule-Child-Carrier-Internal-Adapter/dp/B00FY2ETAG/ref=mp_s_a_1_fkmr1_1?keywords=thule+axle+adapter+internal+gear+hub&qid=1555338822&s=instant-video&sr=8-1-fkmr1