University, online (if you do interesting stuff people will find you), lots of meetups (mostly programming language related meetups), co-working spaces / shared

University, online (if you do interesting stuff people will find you), lots of meetups (mostly programming language related meetups), co-working spaces / shared offices and sometimes randomly in bars. Make sure you talk to a lot of people. Also: a lot of (most?) people are very interesting if you look well enough. Not everybody seems to be interesting, but once you get to know people well, they might surprise you.