I'm a bug enthusiast, so insect specific subreddits like r/moth r/weevil r/entomology
Game ones for all my random niche games I like.
But also I have a lot of health problems so going to those specific subs with my specific problem and knowing I'm not crazy felt really liberating. I know there's a new disability thing on here, but collectively being in a community with the people who have my specific problem made me feel less alone.