@shauna I feel that cycling culture has substantial overlap with progressive politics and meets the criteria for community/connection.
I'm thinking in particular of the #CriticalMass movement, especially in the 1990s. But also of smaller day-to-day things like bike kitchens, cyclists unions, and general advocacy.
I am not particularly active, but through CM I have interacted with multiple local cycling organizations very organically, and I have always felt welcome across these boundaries of multiple organizations, and many people seem to participate actively in multiple.
Near to me, it is very campaign-focused, especially due to the excellent work of the #Boston Cyclists Union who have done so much excellent work. Each municipality also has its own advocacy community focused on its local infrastructure
I don't have any deep insights or referrals to deeper reading on the subject, but readers of #BikeTooter or #FediBikes who have a specific (please!) recommendation might like to chime in.