As a veggie this is a bit of a tricky one, as the traditional foods/meals that have survived are fish or meat centric. But there is one traditional meat dish that I deliberately had once after becoming veggie (my first veggie Christmas):
It’s super good but I had to lie down for a couple of hours after eating it as the first bit of meat in like 6-7 months.
If fish/meat isn’t a problem then obviously Norway has a lot of really good seafood and fish dishes as our country is basically all coastline, and traditional farm animals here are pretty much the same as in the UK (ie. pigs, sheep, cows etc) so lots of local variations on that as well. Cured meats is a very Norwegian thing, for example. Can’t really answer for Sweden or Denmark, sorry.