I think 2 great community activity indicators are - Github issues and of slack/discord/discourse comments. One key thing with github issues in my opinions is that, If the github issues are mostly by the core team, it is not a great sign. You want a large mix of issues from customers or users and not from the team. This is a good indicator if the project is solving real problem or not. Stars is very low threshold action. Same goes with the slack comments, it should have both volume and freshness.