In the days before Reddit 'won' you used to be able to find tons of niche sites/boards cultivating smaller audiences. Beer advocate/rate beer, headfi and whatever the latest splinter was there in the audiophile community both come to mind. There's generally more division by which each might find more 'aligned' or maybe their friends are on one first.
I don't know if it's possible to predict, social dynamics are weird and this is going to be new for a giant segment of the audience.