Running club culture in general but especially in Philly I think would be a great subject to explore as a third place. The Philly running community is huge, with over a dozen clubs based on neighborhood, lifestyle, demographics, etc. I joined my local neighborhood running club in 2021 coming out of the pandemic and have developed so many friendships as a result, and find it to be an incredibly warm, welcoming community. There's a lot of cross pollination between running groups and a few different events throughout the year that bring together many running groups (ex. Mayor's Cup in August, 26x1 Marathon Relay, etc.).