I think you're right that it's 'hygge'-like. Saudade is a common Portuguese word, and (as far as I know) not limited to loving people, but also open to wider nostalgia. It apparently stems from solitatem (solitude). That it would apply to ABBA's music seems to me the result of the artistic-intellectual tendency to re-interpret everything in the opposite direction.
"Hygge" - portuguese living in Denmark - is not related to "saudade". "Saudade" is as stated by others deep longing with a touch of depression and enjoying that. "Hygge" is something you do to have a good time - with yourself or others.
When I mentioned "hygge" I did not mean to imply that they have the same meaning. I was referring to the fact that "hygge" has entered mainstream English culture, to the point where a lot of English speakers know what it means. I was wondering whether "saudade" now has a similar level of mainstream awareness.
