[2023] found solution on killed haralds soldiers glitch!

on the first island to alvadsnes just go in a straight line. do not venture to the left of the island.
get the boat and go to fornberg. ( you can raid ikke & oy island)
then visit valka on the shortest route (via the left) and fast travel back after.
now just follow the missions only

this way you wont get the haralds men killed scene and styrbjorn gives you some goods when leaving to england.

ANY VENTURING BEYOUND THE MAIN MISSIONS WILL RESULT IN THE KILLING SCENE

after you reached england you can travel back to do the side missions/collections