Inspired by a subthread in the post on sci-fi and fantasy tropes. A few books I've liked:
Iron Widow: a YA novel set in a fantasy version of medieval China. The main character has more than one love interest and from what I remember has a nice little spiel about resisting the social pressure to choose. I won't give any spoilers where it goes but I'm looking forward to the sequel this year.
Sing for the Coming of the Longest Night: a cute little winter soltice tale about two metamours that begrudgingly team up to go rescue their respective partner from a magical realm.
The Giddy Death of Gays and the Strange Demise of Straights: a bit of a chaotic story with a whirlwind cast of characters trying to make sense of all the heterodox ways that they love each other, amid a rising homophobic backlash. This one is a little rough around the edges as I believe it's self-published but has great showcasing of some unique kinds of connection. Set in Wales.
As for movies I haven't seen many, but Professor Marston and the Wonder Women is very cute, despite falling into some thruple tropes. Bob & Carol & Ted & Alice gets a shoutout for being a very well-made, early (1960’s) take on sexually open relationships.
What have you enjoyed?
In the expanse group marriage is the norm on earth. The main character has like 8 parents who lead an idyllic life on a ranch in Montana.