There's some open tables games you might be able to find your way into, those are a great way to wet your feet!
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Oh cool! Here on itch?
Also, to be clear, by "open table", do you mean that anyone can join/leave whenever they like? Or is it more like a D&D-style "west marches" sort of thing? (I've used "open table" to describe some of my own games, so I want to make sure I wasn't using a different definition from you.)
A little bit of both, actually! I have two set-aside times where I have 5 open slots for players. I also provide a list of rumors/jobs (it's organized around a neighborhood in a bronze agey megalopolis) - if 2+ folks want to investigate a rumor or take on a job we play.
Folks can bring whichever characters and play whenever they like. There's no real trouble joining late or leaving early during a session, either.
Does that make sense?
I realize belatedly I failed to answer your first question!
All the games I know I discovered by twitter/discord (or run myself). There's also a fair amount of adhoc gaming in the community, especially if you can get down with FLAILSNAILS style play (jumping between campaign worlds each session as a normal thing).