> If people live side by side for 1000s of years, I think that's fair to speculate - there has to be a reason they didn't just assimilate into each other.

Yeah, they had completely different lifestyles that were reliant on completely different biomes. The Norse were farmers, they needed farmland and a little bit of forest for wood and hunting. The Sami were reindeer herders, they needed tundra. Neither could live where the other lived, they spoke languages from completely different families, they had completely different cultural traditions. Neither side had much that the other side wanted. Of course they didn't assimilate, how could they?

But when the industrial revolution came and iron ore was discovered up north, suddenly the desire to assimilate them (or genocide them...) appeared, because now they had something that the people in the south wanted very, very much.

> Though already in Harald Fairhair's day, it seems there were also Sami living among the Norse as boatwrights and smiths and maybe also as wandering professional hunters, hunting livestock predators for bounties - we know that kept going for a long time.

My understanding is that the Norse respected the Sami as a people different from them, and were a little bit afraid of their "magic", because they didn't understand it. They were perfectly happy to live apart, and do a little bit of trade in goods and services. Why go north to raid the Sami, when you could sail south and raid the fat and rich English or the French instead?