Rambling is good for chatting. People tend to mix and you chat with different people, all mixed in with a bit of fresh air and exercise but nothing too rash, like running
I'm not sure choirs are great for meeting new friends, as obviously you can't sit there and have a chat. I mean, I've met lots of people over the years through singing, but it isn't the best way to meet new people.
Agree with WI (or Guilds etc) - though they vary hugely in terms of programmes and age of other folk there. See also Inner Wheel, Lions Clubs, Roteract , Soroptimists (don't know what age you are).
What about becoming a sports coach ? Or a Guider or a Scouter ?
Going to Church?
Joining team of cooks for a lunch club?
Our local Hospice has fundraising Groups that arrange things like Quiz nights
Book club (though tend to be a small circle of people so you won't always 'gel')
This would be easier if we had more info...... if you are looking for weekends / evenings/ / daytime...... if you have particular interests or skills...... etc etc 