Good question. I couldn't see any fuses back there, but in fairness I didn't take the rear panels completely off, because I wasn't sure I could get the rear screws back in. I'd have to do that with my left hand, blind, standing on a step stool. I'm just not that coordinated.
Kudos to you!
However removing the two screws on the outside allowed me to bend the thin plastic panels far enough back to get a good view inside. What I saw was a wiring harness, with wire terminals going into standard connectors, and a small PCB.
I could not see any fuses at all. However I did notice one of the wires was left dangling, and not plugged in to anything:
Is this the disconnected power & ground wires for the Gateway? Could be. Is this just a left-over wire, assuming the wiring harness is a standard configuration shared by multiple units? (For example as you know the 192RBS has an extra set of LED lights for a second tank that doesn't exist.) That's possible too. There could be another explanation that I haven't even thought of yet.
It's certainly possible I overlooked something, but I couldn't find anything that was unambiguously related to the Gateway.
And by the way, the very first thing that I did when I attempted to install the Gateway was to use a multimeter to probe the two power-capable wires, to determine which was power and which was ground. Nothing. I'm confident that I didn't blow a fuse; those wires were dead from the get-go.
I'd love to charge those two wires; then I could remove the 12V DC power/ground wires that I ran to the unit from an AC outlet converter. I color matched the cable covers: tan for the wall and white for the short run across the ceiling. Most people probably wouldn't even notice they were there if I didn't tell them. But of course I know.
The pictures are with the slide not extended, to better highlight where I ran the wires. Once the slide goes out, it's even harder to see most of the wiring covers, because it's hidden behind the slide molding for most of the run. I plug the small AC to DC converter into the AC outlet by the little shelf beside the slide sofa.