Never ran across an RV electrical panel/box on a hinge, and as far as some service length of cable/wire, well, it's an RV so it very's from one unit to another.... no consistency. I had to get behind my panel a couple of years ago (converter/charger mounted to the back of it), mine had maybe an 8" service length and it was a tangled mess, had to disconnect a few wires to get it out far enough to get my hands behind it.
Before you dive into it on your own, give Jayco Customer Service a call (have your VIN handy) and asked them how to get at it, they put it in there
Jayco: 574-825-5861
Bob
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2016 GM 2500HD 6.0L/4.10
2018 Jay Flight 24RBS
2002 GM 2500HD 6.0L/4:10 (retired)
2005 Jayco Eagle 278FBS (retired)
1999 Jayco Eagle 246FB (retired)
Reese HP Dual Cam (Strait-Line)