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.
BBC's Trigonometry was a very sweet story about a monogamous couple that slowly falls in love with their new roommate, and the challenges it introduces into their idea of relationships.
Gemma and Kieran, a cash-strapped couple in busy and pricey London, open their little apartment to a third person. Ray, their latest addition, somehow makes the flat appear larger, not smaller. With an extra pair of hands, many tasks grow easier, nicer, and better with time.
“The traitor baru cormorant” has a main character raised in a culture where polyamory is the norm. Great representation throughout the series, book 2(? It’s been a while) has solid nonbinary representation as well.