At one point when our son was four, almost five, he loved Slow TV, in particular the 7 hour train journey. (We are in Australia so watching it on Netflix.) We'd just put it on for him and he'd play with it on in the background. It is far less annoying than some of the other things he wants to watch (e.g. Commander Keen playthroughs on YouTube). (But, since then, he has kind of lost interest in trains, so it hasn't been on for a few months now.)
https://www.visitnorway.com/media/news-from-norway/finally-t...