The only personal experience I have with it was with men on dating sites (when I used to participate in that) either not putting it in their bio at all, or putting it at the very end and then trying to explain why it's so much better than monogamy.

At one point, I was curious and had several conversations about it with different people (women as well), but just like in the comments here, they always just sound like people who want to have their cake and eat it too. "I want a 'nesting' partner who still takes care of my daily needs around the house, and the ability to screw around with anyone I find who's willing."

The worst ones are the guys who have some kind of fetish about watching their partner with someone else.

It reeks of reducing sex to f***ing which I've never been into. I much prefer to create a deep connection - which if I'm honest, it's hard enough to find ONE person to connect with. It is genuinely impossible for me to connect on that level with more than one person at a time.

Open marriages seem to be a very surface level sexual experience.

It definitely gives the ick.