Paleolithic man would have eaten fruits, maybe rose hips in the winter, and chewed on leaves and whatever was around. Sorry, but I don't see how an all meat diet is mimicking any paleo lifestyle, except maybe those in polar regions, and even the Inuit eat sea weed, berries and other things available in the harsh climate. I don't know how the idea of an all meat diet translates to paleo, when eating would have been very based seasonally. Further, we don't have truly carnivorous teeth nor do we have flat teeth which suggest purely herbivorous diets. We have the teeth of omnivores, so vitamin C should have easily come naturally to the paleolithic humans because they would have grazed on all kinds of things throughout the year.
I expect this to get downvoted, but that won't make any of what I've written. I grew up in the country, playing in fields and woods. As a kid, I learned quickly that you can pull out red clover petals and suck on the white ends to get some sugary sap, and we all experimented with sucking the sap out of tall grasses when we pulled the soft part of it out of the stalk. We chewed on the ends. Indigenous people in many places chew on leaves for medicinal or pleasant effects. All of this supplements nutrition.