I did a very long trip, well outside Europe (unless you could the French WI, which is actually France in Paradise), just after diagnosis. Fortunately, I wasn't on any drugs, so that part was simple enough.
In terms of how others handle it in the sailing community, many have friends or family come to visit them, for sailing holidays, or just plain holidays, and who can bring supplies with them. These days with prescriptions going directly to a pharmacy, somebody just picks them up, stores the meds and transports when next travelling.
For the first time, ever, ever, ever, I will be travelling with medication. I'll only be away for a couple of months this time, in SE Asia, but should I run out of my Meds I'll be able to buy them OTC.
One thing I would urge you to check is that you have a spare meter as it'd be a pesky situation to have strips aplenty, but no functioning meter. On my long trip, I did buy additional strips (which were and remain self-funded) on Guadeloupe, so as I say French WI, so I could buy Sanofi products. Some of the islands had Bayer products, but things were a bit patchy depending on location.
In reality, I'd want a spare meter for the one I'd be using, pluse a spare of something where strips etc., would be available locally (even if I had to pay).
For the sailing community, there are lots of fora, and I imaging the motorhome community would be similar. There's usually a good deal of commaraderie on these places, and somebody usually knows how the land lies where you are heading.
Enjoy! Life is too short to turn our backs on big adventures. 🙂