After months of work on 8.x-4.x (and using it on some of my own production sites), I have decided to scrap the 8.x-4.x branch in favor of 5.0.x and release 5.0.0-alpha1. The code is the same, it's just time to encourage more of the world to use it.

https://www.drupal.org/project/charts/releases/5.0.0-alpha1