There is a medieval Icelandic saga about the earls of Orkney, available in English translation (the Orkneyinga Saga)--it was Norse for much of the Middle Ages.
We visited Fingal’s Cave, and the Monastery on Iona from which much of Europe was Christianized. We were there at the vernal equinox, and the sun went below the horizon for about half an hour, but it never really got dark.
I've seen 50/50 estimates for the highlanders and the non-Sami Norwegians called "Norse".
However, just about 100% of their ancestors came from the Westernmost Ice Age Refugia ~ whether they are Sa'ami, Norse, Celt, or whatever.
You find a slightly different population in Southern Europe, and there's a third group mixed in in Eastern Europe but pretty much the same folks descended from the same folks in the Refugia.
As you move East you start running into populations that left the Refugia and traveled North and went South of the residual ice cap in Scandinavia. They moved East and then South. The Sa'ami differ by going North of the residual ice all the way around the Arctic coast into the Kola peninsula. They also went to America, North Africa, and even tropical Africa. Yet others penetrated all the way to East Asia (the Yakuts have the X factor genes)
The Japanese ruling caste since 600 AD or thereabouts are descended from Yakuts invaders who arrived on the heels of the climate anomaly that shut down China's civilization for the next 300 years.
The Orkneys are different. The native population AFTER the Sa'ami moved through there going North about 12500 BC, but BEFORE the Norse arrived in 1 AD from wherever primitive Germans came from seems to be unrelated to both groups until the arrival of Vikings in about 800 or 900 AD.
That doesn't mean THAT group didn't spread its genes around among the others.
I don't think they've done enough DNA research on the problem to give us all the answers needed ~ first, they've gotta' find the Orkney Islanders. They've been moving out of there in recent decades.