Introvert here so take it with a grain of salt.

But I’ve found having a club/class/volunteer job you turn up to regularly both filters for shared interests, and helps you see the same people repeatedly to get to know them in a low pressure environment. (That last part is hard to do without that regular structure especially when people work a lot.)

Edit: No idea how to take the friendship beyond the club environment but that seems to be something that happens naturally or doesn’t. And just being hobby acquaintances is nice enough