Hmmm I am more of a sci-fi person, but I've definitely still seen some threads talking about fantasy books. I'm guessing you're already on the main book communities like !books@lemmy.ml !literature@beehaw.org ? They are pretty active and I do see discussion on threads talking about fantasy books. There is also the fantasy community !fantasy@lemmy.ml -- which does admittedly have pretty low traffic (though, you could be the change you want to see...). I found one niche community that was very recently made !cozyfantasy@wayfarershaven.eu

I get how hard it can be to find active book reading communities & wish I had more suggestions in the fantasy realm. If you have a specific sub genre in mind, search for it or maybe even make a community for it. I was surprised to find a few different scifi sub genres already had active communities on lemmy & even recently made communities are growing fairly quickly with the new users.

Good luck finding your next page turner & lmk if you want sci-fi recs :)

Edit: to add and un-add exclamation points