Join a club for people with common interests. Or find a new interest - I started CrossFit 2 years ago with no prior interest in fitness and to me the social aspect is as important as the fitness aspect, if not moreso.
There was a weekly freestyle dance in New York City that I attended, many years ago. In a studio, with a good wood floor, near Broadway and Houston. It was run by a collective, and part of a northeast association, which had summer dance camps. As I recall, it cost $5 at the door, and less if you subscribed. All ages were welcome, even toddlers. Maybe it still exists. And there are many others, for different dance styles.
But none that are so completely unforced where you can just show up once a week for no reason and be welcomed. Or so it seems from the outside.