Yeah, it’s a very common thing here in Northern Europe too! At least my corner of it. Even growing up in a very remote and small village in the Lappish wilderness a burger with pineapple was one of the more common ones at the local (and the only) grill-kiosk.
However, for whatever reason, pineapple in a burger seems to be almost always paired with a fried egg. I think it’s great but not really sure why exactly that’s so common a combo.