Turns out all the methods humans used for the few hundred years before smartphones still work!
I met most of my friends at hackerspaces, board game nights, conferences, giving conference talks, parties, bars, etc. Put yourself out there in spaces where human beings of likely overlapping interests exist and you will make the friends that matter most. I first had a conversation with my wife of over a decade by tagging along with a bunch of strangers to a random pizza place. My wife did not use dating apps at all, so in person was the only way a guy could have met her.
I also open my house once a week to anyone I know, and host events every month or so. Met a lot of friends-of-friends that way.
And look, I get it. Doing all that is scary. I still have a lot of anxiety about hanging out with people I do not live with, and I do it anyway. Never regretted it once.
Spending time around other people in person makes us better people.