Huh, I was not aware that “stuga” is swedish for “cottage”. In norwegian, cottage would be: Hytte, hytta/hytto/hytti, hytter, hyttene. I could include genitive as well, but it’s just adding an -s to each form.

They are dialects, mostly. In parts of western norway, -o is used for singular feminine words, for example: “stuo” (instead of “stua” (“the living room”)). Similarly, -i is used in parts of central Norway, for example: “boki” (instead of “boka” (“the book”)). I’m not sure if these are accepted in “correct” written form of nynorsk, but it is commonly used in spoken and written dialects.

Norwegian: -en, -a, -et (suffixes)

But also -o, -i and probably other variations depending on location.