"searching for groups to join that are at least adjacent to my interests." Why limit it even to these? To extend your analogy: if you're about to fall over dead from starvation, you'd accept most any food.

Common hardship is great for quickly cementing group relationships. You could volunteer time at a charity that will throw together a random group of people at sweaty, repetitive work for an afternoon. You could join a sports team and coalesce around hatred of your rivals.