I have some questions for you,OP. Have you ever gotten in legal trouble in your current domicile state due to domicile issues? Have the domicile police forces of your current state rapped on your door lately to see if you actually sleep there? Do your domicile police care if you use a PO box for your mail vs. having it delivered to your door? Or do they care if, when you travel, you have your mail forwarded to another address? Would your current domicile police care if you had all your mail forwarded to, say, your CPA? When you leave your abode for an extended vacation or trip, do you have to check in with them? Do your domicile police check your credit card receipts for in state vs out of state purchases? Has any of that ever happened to you?
Just cause you're going to be full timing in a RV and living, according to some, an unconventional life style, doesn't make you more of a 'suspect' than anyone else. Domicile is not necessarily where you sleep. It is where you intend to return someday. You can have that intent even and then change it to another intent before fulfilling the first intent. Most of our congress people spend more time in DC than they ever do in their actual sticks and bricks. And I suspect by far most of their mail comes to their congressional offices whether in DC or the various 'home' offices than ever goes to their actual S&B house.
Claim your state. Do the things that you do now in your state. Get an address. Get insurance; get a D/L; register to vote; get your vehicle(s) registered and plated and inspected if needed, change address for your health ins or get new health ins., etc. Then chill.