I have never heard of any RV that doesn't have fuses for 12V power. Check the auto resetting breaker close to you battery. That would be the first step. This controls all power coming in and going to battery. Make sure you have power on both sides of breaker. (small square box with studs. wires connected to both sides. These fail all the time. also check for wire corrosion on the wires. Are they loose? Loose wires can cause dim lights.
Dirty frame ground from battery is a common issue as well.
Look at what is missing. Like does the fridge power up on 12v/propane (that portion is 12v)
Also take a picture of your breaker/fuse panel with doors open. Post it here and we can help more.
Victron Energy inverter/charger, 1240w solar
550ah LifePo4, Microair Easy Start,RVLocks (keyless)
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2015 GMC LTZ,6.2 Gas, Short Box, Firestone F3 air ride.