The approach that Yukimura is taking in the current arc is very rich, knowing how rare is for mangas to portray an expedition and the beginning of communication with natives, we will have a new character from some tribe at some point, which is great and brings a third perspective to the story.
Months ago I was confused as to why skipped a trip to this arc, but I remembered: the author just wants thematic consistency on the theme of violence, I can see the possibility of having 3 conflicts, the first would be the tribes themselves having a rivalry among themselves, the second would be Thorfinn's crew against the local tribe and lastly a civil war caused by Eyvar challenging Thorfinn's leadership. Not many people do theories here, but I would like to share my thoughts.