An entirely side comment: this issue is touched on in the quite entertaining Norwegian show on HBO Max, "Beforeigners." I recommend it. It's a sci-fi / police p

An entirely side comment: this issue is touched on in the quite entertaining Norwegian show on HBO Max, "Beforeigners." I recommend it. It's a sci-fi / police procedural with the premise that people are suddenly arriving from the past (the 19th Century, 1000 years ago, and pre-historic times). It also has a fair amount of humor throughout. The time-travelers from 1000 years ago commonly refer to themselves as "Vikings," although one such person testily observes to a person from the present, "actually, we prefer the term 'people of Norse descent.'"