If you’re into JavaScript, https://github.com/dynamoose/dynamoose is a project I maintain, and has a lot of great documentation, Slack channels, and more.
Although my attention on it goes in waves, it could for sure use more help. I’m also totally willing to help answer questions and point people in the right direction.
We currently have 80 open issues, 6 open PRs. 9 of those issues are marked as “good first issues” and 8 are marked as “help wanted”.
So there are for sure some easy jumping off points to get started. But I’m also always happy to answer questions and assist in anyway I can as well.
Beyond that, it’s all about diving into something. I found Dynamoose when it was much smaller, and just started with small contributions and built up from there. Following developers on social media, and following programming communities and newsletters can be helpful too.
It’s not really any different than hosting any other service.