Each meetup group is different. you might find a group very welcoming?
Volunteering is another great way to meet people. It may depend upon what you choose to volunteer for? Many towns/cities hold public events where they rely upon volunteers for the event. The local United Way also usually has a list of specific volunteering opportunities.
If you choose a volunteering opportunity within a field which interests you, you may find friends with similar interests.
I don't know how you feel about churches/spiritual groups? Many of them, especially the larger ones, hold all kinds of events. Many also have special group activities geared toward single people, as well.
Maybe join other social groups of interest, ie: a camera club, a walking/hiking group, an exercising group, an IT group, a skiing club, etc., etc.
Just a few ideas.

WC