Hate to break it to you, but making any friends in/past your 30s is very difficult. But I do get your point that choosing childless makes it even more difficult. I’m lucky enough to have had a couple of close friends who chose to remain childless before I had kids, and we are still close. But we would have remained close in any case.

I’m in my 50s now, and maybe I’m an asshole, but the last time I made a new friend (a real friend, not acquaintance) I was in my early 40s, and that friendship did not survive me moving an ocean away, to my great sadness. This happened with me several times starting in my early 30s, but I’ve moved continents three times, so mostly my fault.