**Beware, rampant speculation**
I don’t have any direct evidence, but the more I read about early modern Finnish food and foodways, the more I suspect that the Finns remained more culturally isolated (due to language, geography, politics) than did the rest of Scandinavia, and thus that early modern Finnish food can give us more insights into what Viking food was like.
Again, this is just speculating, but early modern Finnish cooking relies heavily on forest products, fish, unleavened or sourdough breads, cultured dairy products, wild game, and fermented food and drink.
Also, there are a lot of examples in early modern Finnish cooking of utilizing all parts of animals at harvest time (blood soups, blood dumplings, offal soups, blood porridge, many different sausages, etc.). There are also cooking techniques such as cooking on stone hearths, cooking fish wrapped in newspaper (read leaves or wet straw) in an open fire, and brewing traditional beers using hollow logs and juniper branches that may well be holdovers from a much earlier time.
Your mileage may very, of course, but I think it’s worth considering…