This does not directly answer your question regarding a 2015 2861DS, but my 2017 2861DS has a Progressive Dynamics PD4560 converter/control panel, it is a single unit with the converter, breakers and fuses. It is located under the bed and it also has a LED indicating charge state that is seen by opening the door on the unit.
Have you removed the wood panel covering all the stuff under the bed? You will find the water tank and transfer switch there on mine and maybe the separate converter on yours? The panel is secured with just two screws, you need to prop the bed up to get to it.
2017 Forester 2861DS
towing 2015 Jeep Rubicon