I've heard that https://up-for-grabs.net/#/ is a good place to look to find projects that have issues that are beginner friendly.

JIRA and Slack.

We started off with just the development team using Slack, and the rest of the company using Skype. Now we all use Slack internally, and Skype when that's all clients have.

I think the reason that the company moved to Slack was cost based, but really I think they wanted to play with the integrations :)