In my opinion, Pivotal Tracker was the collaborative planning tool with the best feature set, usability and presentation. It was highly opinionated, but on the flip side gave you a baked-in process that just worked (at least in my team (1 product owner + 3 developers)

A while ago, there already was a discussion on HN [1] about a list of projects that implement PT clones [2].

Does anyone here use one of those? Which one did you chose and what are your experiences, what is still missing?

[1] https://news.ycombinator.com/item?id=43378925

[2] https://bye-tracker.net