My advice is start really small and low commitment. I choose things that I'd either enjoy even if I spoke to no-one once there, like a crafty workshop or something that would be good for me mentally/physically like a yoga class. Make yourself go once, and if you don't like it, tell yourself it's only an hour and you don't need to come again. I tried loads of things, some stuck, others didn't. If you feel anxious about big groups of strangers, try something were you know numbers will be limited to 10-12 people like a small craft class or a book group.
Get something in your diary every week, or maybe every fortnight if that feels more manageable. The things I found best were a couch 25k course with a local running group...no pressure to talk, but lots of social opportunities for drinks afterwards/park run/extra runs etc once I got into it and a local walking group where I found a couple of women who wanted to meet for extra walks/coffee on top of the monthly group walk. If there's a WhatsApp group, join it as they'll be extra social events that people start adding.
Depending on your interests I found these sites helpful for giving me ideas of things happening locally.
Meet Up app
Class Bento
Events on Facebook
Eventbrite
Local adult Ed courses through council website
I also made a list of things I wanted to try/places I wanted to go and tried to do one a month, even if on my own. I posted pics on my Facebook and before I knew it I had old friends messaging asking if they could come along next time I went outdoor swimming/to an exhibition etc, which has been lovely for reconnecting with old work colleauges/distant cousins etc.
I'll be honest there were some things that I wasn't bothered about trying again, but there wasn't anything I regretted turning up to. After the first few times tipping up on my own, I started getting used to it and people are more likely to chat if they see you're solo.
Summer is a good time to start, as the light nights make it easier to get out after work. I found it helpful through winter to have something where I was meeting someone planned, to make me go out as they'd be expecting me.
Sorry super long post, but your story resonated with me, so hope it's helpful. You can definitely do it!!!