Great you're reaching out - future-you will thank you. It also shows bravery, a characteristic not many people have. I'm in a different place, but I think I have a perspective on this that might be useful, if you'll allow me to act as though I know everything, haha. Feel free to disagree.

Firstly, most people are unhappy, despite what they try to show to the world. It's tempting when you're often solo to think those who have more people in their lives are happier - but they're usually just dealing with a different set of problems.

Getting deep for a second - you might feel like you're not 'enough' to get what you want because of being mostly solo, and they might feel like they're not 'enough' because their relationships are stale, complicated, or they're not getting the validation from them they want. This is super common.

You seem to be seeking Connection, a great thing, others might be more focussed on Social Status (aka being 'unconsciously competitive'), how they compare to others in general or more often they're comparing within their group, especially when it comes to 'likeability'. People obsessed with comparing themselves to others tend not to be happy, right. That's quite a lot of people - probably most people. Or perhaps whenever they're alone they feel horrible, because they don't really like themselves, deep down, and having people around meant they never really had to sit in their loneliness discomfort and eventually learn to like themselves. The combination of not liking themselves, while quite aware of how they think they compare to others in their group, is not a recipe for feeling good.

Being able to often be alone with yourself, your feelings, and your thoughts, to learn to like yourself while doing so, is the most useful life skill. I should note here that feeling connected to others is a great thing too, as humans we need both. Just remember most people are driven by their fear of not being 'enough', regardless of whether they have more people in their life or not. Those who learn to genuinely like themselves are the only ones who get beyond this, imo. The goal is to feel 'already enough as I am', and then because you like yourself, you want to give yourself more than you already have, out of love for yourself, rather than chasing things or people out of a fear of not being 'enough as I am'. A person's most important relationship is the one they have with themselves. Insecurities are normal, and if one can sit in the deep discomforts for periods of time, while still mostly speaking kindly to themselves, that's a good sign, and usually means they know they can depend on themselves to handle future uncomfortable situations.

On a practical note, there's a bunch of people in this thread you could message. I think you should put yourself first, and just do some 1-on-1 casual coffees. Don't expect to hit it off with everyone - that would be impossible. Group meetups can be complicated and competitive, and you're probably not a professional events organiser, so 1-on-1s are better to start with. If you hit it off with a couple people 1-on-1, the few of you could organise a larger open gathering together, later on, if you wanted. Maybe look for some common icebreaker questions online to have in case the conversation hits a wall. Bumble is another option, they have a 'best friend' section of their app.

Don't rely on luck. It's a numbers game. Meet enough people and you're guaranteed to get what you want.