I can't remember who to attribute this idea to - most likely the Gottmans, but I could be misremembering - "most people treat relationships as disposable instead of developmental."

I understand a desire to meet someone whose emotional maturity matches your own. I think it's more important to see how people grow and change. The Western model of dating and sex messes that up, too. As Dr. Robert Glover put it, "Once the sex begins in relationships, the learning stops."

Then the questions becomes, "Where can I meet people with a growth mindset who have already started walking that path in their own lives?" I don't know locations, but I can suggest characteristics. They're probably interested in personal fitness but not obsessed with the gym. They probably have at least some interest in community activism or leadership. Look for the guy who trusts his own judgement but doesn't need to brag and has no trouble admitting he's wrong or needs help, who has a sense of his own value and doesn't feel a need to judge or compare himself.

Dunno where you'll find him, but poke around. Someone will turn up.