Related, many small(-ish) bars have a stage for live music on Friday/Saturday. There may not be enough seating for those nights, and there’s little/no standing room, so people randomly share tables. From there, you strike up conversation with other fans.

Find the small places where they advertise the bands by name, and make sure they aren’t just cover bands. Irish pubs have been lucky for me, but there’s another place near me that regularly has jam bands.