That's advice to meet activity partners, not friends. Think of your closest friends. Did you set out to meet them by looking for people with their exact interests? Maybe you did and you and your friends are part of a scene, but I'd bet most people did not.
On advice like yours, I started a niche club and ran it for 3 years. When people join your club, they're not there to meet you! They're joining to participate in the club. Now you're in the awkward position of responsibility as the club's host/organizer, with the additional distance between you and the other participants.
My closest friends came to be because I spent significant time around them.
>The main catalyzer is something you do regularly with another person.
The easiest thing to do that in an intentional way is to find regular activities and do them with other people. The activity is the excuse to be together for x amount of time every week, be it whatever. If you choose something you genuinely like, not only will your intent be more sincere but even if you didn't meet anyone, at least you did something you enjoyed.
This is advice for people who have zero or one friends. If you already friends, then, by definition, you don't have this problem. Also, a bit controversial but useful, people who don't have this problem usually give very poor advice to people who have it. "Just make more friends, bro".
I'm curious to hear if you can think of a better way to make friends irl with a decent chance of success.
>I started a niche club and ran it for 3 years.
Did you not make one single lasting connection (friendship) from that?