In another HN post[0], the top comment mentions Nestfull[1]. Is that a viable candidate to replace Pivotal Tracker?
It provides a Kanban board with swimlanes, but the UI is unique AFAICT, because items in the swimlanes can be entire Kanban boards themselves.
Regardless, I'm going to try it for personal projects.
[0]: https://news.ycombinator.com/item?id=43362725
[1]: https://nestful.app