I'm an American in the process of getting a Danish work permit, and it's easy so far, but they seem to have a special fast-track category for "researchers", and a Danish university is sponsoring me. I assume I couldn't just move there on my own. On the other hand, Linus also fits a fairly easy profile, so could probably get a work permit almost anywhere (highly educated and internationally famous engineer with steady employment).

Getting Danish citizenship, though, is notoriously difficult, and among other requirements, they require you to renounce any other citizenships (unlike the U.S., they actually enforce this requirement). Many foreigners, as a result, live in Malmö, Sweden and commute to Copenhagen (it's about a 30-minute train ride over the bridge/tunnel), since Sweden's citizenship laws are more lax, and once you have EU citizenship you're essentially good anywhere in the EU.