If it has an issue tracker, you can look in there for things that look like real issues and are unaddressed.

If there's no issue tracker, you can YOLO and try it and see if it works, or you can look around at the code and see if it looks reasonable.

Even if there are unaddressed issues, you can always use it and fix it when it breaks. If it's reasonable enough, it's a good start anyway. And at least my assumption with open source is I'm going to be fixing it when it breaks, so lack of a pulse is better than churn.