Mostly on technologies that enables people talking. My first online friends, were from using IRC; I even made local friends, I would never without using the online way. Then I made friends using simple emails to far away people. Next I remember I did a lot of friends using SecondLife, were i found out about "mein sonnenshein", a virtual friend i virtually married 4 times and divorce four times also (it was very cheap like 10 cents to marry and 25 to divorce, lol) and a lot of other good friends; last one i got it in a MMORPG where i saw a "beautiful" elf warrior and started talking to her, and it results she spoke the same language and were in another continent. There is been a lot of time over, but i still make contact with some of them. I would dare to say that the virtual friends were as good as the real ones, because in the end we are all humans and connected with language, and resonate in many ways.

Reddit hasn't really facilitated friendships (let alone the kind leading to real-life meetups) since the 2018 redesign at least; even before that the site was remarkably impersonal compared to any old-school forum.

You have to join a more restrict community such as the FIFA PRO Clubs or the Rainbow Six teams or whatever is restrict and gaming thing . The general chatter/board where a plethora of people hangout such as reddit won't get you anywhere just like real life

Discord's not a bad way if there's a shared interest. I met some great people on a server dedicated to a hockey team. We'd all watch the game and blather away in chat. You get to know them after a while.

For me, it was a Twitch chat community. It started with everyone showing up the same time every week to watch a couple of people who streamed together. They eventually started a Discord server when Discord became available (which decreased the closeness of the actual Twitch chat community in some ways by making it all more asynchronous, imo, but did also solidify the community beyond Twitch in other ways). I've been to several meetups where I met many of those people, and have also separately met the two streamers a couple of times as well. I consider a number of them "online friends" to a varying degree.

I think something like Reddit would be unlikely to lead to this sort of thing, unless you're regularly participating in a small enough subreddit in a consistent/repetitive manner so as to recognize and be recognized by others (for example, I once helped run a little fanfic book club in a show's subreddit, and if that had gone on for longer, then I could see myself having gotten to know the other co-organizers a little better).

The key is probably to have some shared interest to bring you to the same place, but also an environment that's flexible enough to sometimes talk about things outside of the main interest. Older forums that would have an off-topic board were probably better about this than Reddit, since Reddit tends to segregate discussion about different topics into different places (with different people).