Both of the long-term, meaningful relationships in my life were with people who like me, just didn’t happen to get very sexually jealous. So while we weren’t exactly polyamorous, we did sometimes have sex with other people — just for fun. The “rules” were, no emotional involvement.
That worked for me OK, just because that’s how I am. I’d have been happy to be monogamous if it mattered to my partner.
Different strokes … pun intended.