Clubs and volunteering. Even at a homeless shelter or similar.
Volunteering is especially powerful because you are implicitly “supposed” to be there. Your presence is already explained and accepted, due to the service mission of the volunteer organization.
Therefore you have already achieved the first step of building friendships: shared experience, and shared time spent. Now that those are established you can step out beyond that to get drinks or pursue a then discovered shared hobby, like cycling or hiking or gaming whatever.