Ok, so on my NOBO 19.1. I installed a second TV right off the cabinet, very similar to your setup. So the first TV is in the hallway similiar to yours on the pic above the dinette and the second I used a articulating mount, and drilled a hole for the wiring in the cabinet and ran the wires through the cabinet to the second TV hookups and it worked just fine. I have included some pics of what I would do.
My NOBO is 28 ft long but its similiar setup and layout to yours.
In the pic where the bed is. You could put in a second TV right there and it will go flat against the wall, mine did, but the mount goes off to the right and adheres to the cabinet and the hole in in the cabinet. This hides all your wiring and keeps you from having to find the aluminum stud in the frame, you just use the cabinet. I used a 22 in Roku TV and I want to say that was the smallest ROKU I could find. All wiring is hidden goes into the cabinet runs all the way through the cabinets about 6 ft through to the next set of cabinets to that TV's hookups, so I have 2 tvs. The factory one I think is 24inches and I installed a ROKU box onto it also.
Forest Rivers only mistake was the TV that came with the trailer does not swivel up and down, only side to side. You need for articulation and the ability to lock it. Mine has set screws that are thumb driven and lock, so look for that feature that way it won't flop around going down the road. Also place a fabric pillow case over it when on the road. You can buy actual TV covers that are like shower caps also , my wife found one, big fabric one that stretches over it keeps it from bangin the walls if you forget to lock it down, which will happen.
But you say, do I really need 2 TVs while I camp. My question is, "Why did you stop using a tent then?". I bake cookies also in my oven while camping. We like to rough it.
Here is a link to a similar mount I used except mine has "butterfly screws" that you can twist and lock with your thumbs so you do not have to use a screwdriver everytime you want to lock it in a different position, also look for that feature. I looked and couldn't find the one I ordered.
https://www.amazon.com/Mounting-Drea...s%2C111&sr=8-5