Many DLCs of Banner Saga 3
aren't working on GOG. Several time ago I reported the problem to GOG support and Stoic support, but although the Stoic representative was very kind and even GOG promised to investigate, nothing was ever done, and Stoic seems more busy creating their new MMO or whatever rather than fixing the many bugs in the game, so I don't think they will ever do anything.
According to my tests, the DLCs that don't work are: Legendary Edition
- Exclusive Heroic Title - 'Shadow Walker'
- Exclusive Legendary Item - 'Petrie Clan Ring'
- Unique Dredge Item - 'Sculptor's Tools'
- Unique Hero - 'Kivi'
- Unique Heroic Title - 'Shield Cleaver'
In order to get them in the game you have to reach a certain point in the plot, so it's not super easy to confirm their presence, but I have tried to test them in many ways and have never been able to get any of the listed items or characters. It would be better for someone to test them independently, but I don't know anyone who has all the DLC, let me know in case.
Also, the GOG version never really had the Eternal Arena
leaderboards, as is fraudulently reported on the DLC page instead. The button to see the leaderboards simply doesn't exist in the GOG version. This probably breaks at least one achievement since it requires being first in a leaderboard that doesn't exist on GOG.