I found it very difficult to get vehicle insurance appropriate for a full timer. I went through an insurance agent who specialized in obtaining those policies and still found out my coverage was insufficient. I am not sure who to recommend at this time. Beware of insurance agents. Many do not even know the coverage that is appropriate for a full timer.
As you found many institutions, especially banks, financial, insurance and even Medicare, require a "permanent" address, not a PO box. BTW, if you have a choice, South Dakota is the better choice and the State policies are very accommodating for full time travelers. In any case for our checking and bank accounts and other financials, I went online and changed the mailing addresses and had new checks printed with that address. For the new address, I specifically omitted "PMB" and only included the actual number as if it were an apartment number. I never lied but again just did not include PMB. Make sure you also do this for your printed checks.
You may also find there is another address available to you. When we physically went to South Dakota to make DMV and other changes, we had to stay one night at a campground or motel. That became our official address for voting and for some other State purposes. Our mailing address was actually in a different county but that did not matter. If absolutely necessary you might be able to use that address as a permanent, physical address. We were never in that position when omitting the designation of "PMB".
