According to other posts you have a 1999 Travel Supreme
So it would have regular 120V AC system (AC Panel with Main Breaker and then Individual Circuit Breakers for Outlets, A/C Unit, electric elements in fridge & water heater, microwave and maybe couple of lights (bedroom/dinette---MAYBE)
And then you would have a 'Converter' that would supply 12V DC system and recharge battery when connected to AC Shore Power (or generator).
Not connected to AC Power then battery would supply 12V DC System'
12V DC SYSTEM
Would be water pump, furnace, landing gear, slideouts, fridge controls, water heater controls, exhaust fans, LIGHTS
22V DC......measured using a voltmeter set to DC??
Do you have 2 batteries?
Are they 12V batteries?
Are they connected in parallel (POS to POS/NEG to NEG) or in SERIES (POS to NEG)?????
Series would give you high voltage readings but it would also cause issues with 12V items.......lights really bright, control boards fridge/water heater/furnace burnt/damaged etc.
Need to figure out that 22V reading....ASAP!

Fluorescent lighting.....
That is a 120V AC lighting (plugged into an outlet)
So you would need to install a 120V AC Fixture and plug it in to outlet
Install a 12V Light Fixture and wire it to available DC Power (pull new DC wires etc)
OR inform wife.....it is what it is HON