Utopias are an interesting thing, and quite often a topic of lots of sci-fi. (And their more dramatic half dystopias.)
Atlas Obscura has a great map of failed utopias in the US.
I was kind of surprised by the nudist colony in the 1900s. And apparently not just one of them but there were lots? What? Huh. It does reinforce the idea that we just aren’t that shiny or new. There are lots of things that seem progressive that have much older roots.
I did get lost in the wikipedia article on utopias, I’ll just share the list of fictional ones.
They are nearly always used as a background for satire, political or philosophical discourse. I can’t think of anything that is a true utopia (not a GASP! It’s really dystopian!) that is a romance or is a thriller or a myster. Utopias must have romances, but maybe they don’t have the misunderstandings that lead to drama? Hm.