They were ynited until '05 apparently: https://en.wikipedia.org/wiki/Dissolution_of_the_union_between_Norway_and_Sweden
I get that it’s more of a nostalgic dream than a hard-headed practical policy. But if I did a poll would it be a popular opinion there?
I don’t know specifically about nostalgia, but whenever it gets polled, Support for a Scandinavian federation is fairly high, I think consistently higher than support for joining the EU in Norway.
https://fiia.fi/en/publication/the-blueprint-for-a-nordic-federation https://ukandeu.ac.uk/is-norway-edging-towards-a-fresh-eu-membership-bid/
It doesn’t get polled that often, since no government is interested in such a proposal,