The Fediverse is the first place in 30+ years I've found many folk *both* into FOSS and /also/ actively into left wing politics.
Previous to that most FOSS users I encountered were perfectly happy with capitalism / neoliberalism, particularly the "petit bourgeoisie" kind, and only seemed to dislike GAFAM as they are better at capitalism (often just by giving users slightly more of what they actually want)