

Drying can work to a degree if it’s cold, but it really depends on how you dry it since vitamin c is water soluble. Anything heat dried(including sun dried, which over temp and time will oxidize the vitamin C) is out and osmosis like salt drying can bring the vitamin C along with the water into the salt. Modern sauerkraut is often pasturized so that’s pretty useless for vitamin C. Finally canned preserves are canned under high heat. These industrial processes are a major reason why scurvy was so hard to treat at the beginning of the industrial revolution. Nobody could figure it out because they kept heat treating potential solutions. The British pasturized the lime juice at one point, for example.
Yeah sailors had jerky, smoked meats, and dried meats and still got scurvy. Hudson Bay colony had pemmican and still had scurvy outbreaks. The problem is most of the sources you noted destroy much of the vitamin c. Pemmican is a super food for macros but sucks for micros and still needed some forage to supplement. Famously the Iroquois would use tea made from eastern white cedar to do so.
On your glut-4 note: glut-4 is important for cellular transportation and diabetes can harm it’s use leading to oxidative stress but it’s not significant in uptake from food to serum which is the important part when we’re talking about dietary vitamin c. It’s also really incorrect to say glucose wasn’t a factor in ancient diets. The Romans marched on porridge and bread. High carb diets are a defining feature of the neolithic and beyond.