That cut bundle of wires under the sink appears to have the same colors as the ones cut up front under the couch, right next to the hole in the floor.
I think that bundle was the original tongue to trailer wiring, including both the tail lights
and camper 12 volt system since I see the white and black wire in those bundles at both ends.
Does not mean it did not have an inverter because that might well have been hooked into the same 12 volt line as the battery
on the tongue coming back in the bundle of cut wires. A really old inverter I had acted as an auto battery
switch. All 12 volt came from there and was either fed from transformer of converter or line running to battery
. Had an I kid you not actual relay you could hear kick over when you plugged in.
Yep getting an electrician over will make short work of the whole thing. Might start considering where you want to have outlet(s) and lining up some parts. Under the sink is sort of inconvenient place to plug in a laptop but works great for the fridge and the converter.
Notice in that picture there is a second unused place for a circuit breaker so you can add a plug or two where it will do the most good, outside by the door is a popular choice or the end of the lower kitchen cabinet. Oh and adding GFCI outlet to the end of a line will make it a lot safer.