Good find! We updated our article about this to include that song as well! halfglassgaming.com/2020/11/is-this-longship-song-from-assassins-creed-valhalla-a-haunting-tale-of-broken-friendship/
Is there an official name for this song? Or a OST I can download cause I love this song and the sea shanties in this game are just as good as Black Flag(imo)
I've not been able to find one for the Valhalla version, but someone else left a comment about the original (Norse) version of the song if you're interested in that.
