I saw a few at Starbucks. Look for the people with laptops on stands wearing headphones filling out applications on LinkedIn.

I've had some success going to https://lu.ma/ events. Meetup.com is dead but we've got a new kid on the block. At least for SF it's working great

Who are you and what are you trying to sell me? :)

Here.

Contributing to open-source projects perhaps?

I'm at home drinking.