My local roleplaying game club. I'd bet half of them, despite not acknowledging it, are considerably deep on the spectrum. Funny bit: My aesthetic ideals clash with those of one of the guys there: he likes things to be well-ordered in neat piles and I like non-patterns. Doesn't stop us from being good friends.

I meet people in the spectrum at work, unintentionally.
IT sector, a magnet for people like us.

I've been having such a hard time. I think that I have unknowingly built a life of insisting on environments that aren't good for us, so I haven't had much success. Still, I have found some by staying vigilant for autistic traits. Once I notice them, I try to be near them more often so that there are opportunities to engage. If they come up, I try to engage with something that is autism friendly, like pointing out how loud it is or asking a question that shows I'm trying to thoroughly understand an ongoing topic. Basically, I'm will ask something to try to get any interaction and unveil my 'tism, even if it isn't engaging. If I can't think of anything, I can compliments something of theirs that doesn't follow the standard trend, especially by focusing on a specific detail (e.g. I like the color of your cool glasses; they match well with the hat of the guy on your shirt). My aim is to establish recognition of each other in case more opportunities come up in the future. It's slow, but seems to be working. A major limitation that I have experienced with these environments is that they don't really leave us with much time to engage each other in autistically meaningful ways (i.e. deep conversations). In the rare cases that they do, we might have already expended our executive functioning fuel on sensory stimuli, navigating the social scene, or whatever else we've had to endure.

The other avenue I'm trying is something I've been learning recently. I would like to get into autistocratic (made that term up right now, thank you very much) environments, but it's been hard for me to get my foot in the door because I would have to break the door to put my foot in it (jk! lol 👉😉👉). But seriously, I have difficulty going to new places by myself and starting conversations with people. I end up coming off a bit odd to others. Anyway, I found a group for autistic adults through a local organization that provides services for autistic people. I've only met with them twice, once virtual and the other in-person. It's been pretty nice so far, so we'll see where it goes. Maybe that will lead to other autistocratic spaces, either through recommendation or invitation. I'm hoping that I will eventually find a space or group with lots of us so that I can have many opportunities and diversify my social network rather than depend on just a few people or groups so that I'm more socially adaptive and stable.

Fyi, this instance has a Matrix chat room that is pretty active. Maybe it will help to join and engage with users there. Relevantly, your question is a common topic in there. Seems like many of us have trouble finding each other in-person. Here is the link to the chat room.

Random places. For best results avoid routine, people are everywhere.

Constantly trying to force myself to do new things. It's hard. Life is hard. Gotta try.

Computer science courses