I'm also a bit shy, but what worked for me was to start making a serious attempt to attend Meetups for things I'm interested in (and even some things I wasn't, just to try them out). There was a two year period in particular where I attended 2-4 meetups a week. Most of my main groups of friends I have now I originally met from Meetups.

A couple key things that I think made it work out for me:

1) Once you find a few groups with people you like, keep going to those group's meetups. It's not that important how much you speak, but how many times people see you. Repeated exposure seems to lead to people just recognizing you and being happy to see you. I eventually learned a bit about people just being around them at a dozen or so meetups, and you start knowing things to say to bring up conversation if need be.

2) Choose meetups with activities. That way it's not a big deal if you don't say much, you can mostly just focus on the activity. I've had good luck attending meetups for board/video game nights, movies, hikes, mini-golf, scavenger hunts, karaoke, trivia, etc. If you go to enough of those with the same group, you'll give #1 a chance to kick in, even if you barely say a word.

3) Try not to be annoying. This sounds more daunting than it really is. I actually was an admin of a group before (took up the reins after the original creator left), and there's a handful of things that caused drama with individuals in the group that people complained about, so if you don't do anything in this list you'll probably be fine:

a) hygiene (yeah some people never really showered before and smelled pretty bad, there was a couple in particular that were both consistently smelled bad that people hesitated to host meetups because they didn't want them to come, and privately complained to me about it)

b) making unwanted sexual advances (However, I've known many people who have coupled up from meetups, so you should feel free to ask someone out, I just wouldn't advise trying to directly hook up with people at meetups, especially activity meetups. bar meetups might be a bit different expectations)

c) having a toxic or hostile to other members personality (like we had one woman that got pissed and yelled and spammed admins whenever they scheduled something that didn't fit her schedule, as an example).

d) not respecting people's property. don't go overboard getting drunk and start destroying shit, or if you're playing someone's board game, don't get greasy fingers and then handle/bend playing cards in the game, etc.

Actually being the quiet, easy-going person in the group is probably good for longevity, as long as you shower before meetups :)

Me just doing these things led to eventually people inviting me to private events outside of meetup, and once that starts happening that will help lead to more friendships (like my main friends don't even really use meetup groups anymore, they just invite people they met from them, like me).

I hadn't done in-person meetups with strangers for the past couple of years because pandemic, but I did start going to a couple meetups again recently, and it seems like I might be able to use this strategy to meet some new interesting people (there's one group in particular I liked hanging out with, I'll start going to more of their meetups).