Evan, welcome to MA!
There is a an Appalachian Mountain Club group that hikes every Thursday evening in Blue Hills in Milton, just south of Dorchester and accessible by public transit (train then bus, or train and bike). There's over 200 miles of (official) trails to explore in Blue Hills, and this group hikes them all. They're easy 2-hour hikes but the best part is connecting to a community of hikers in the area (a number of whom have done thru-hikes or are planning them) with great info and a desire to do trips. Most are traditional backpackers and bring traditional equipment on these short hikes for conditioning, but I've met several ULers...including a guy who makes his own incredible backpacks and a gray haired guy who hikes with an umbrella who goes by the name "Ray".... :)
PM me and I can put you in touch with them if you're interested.