I don't know about animation, but it seems the UI system and their widget library was overhauled.

"The Feathers widgets have migrated to BSN, Bevy's next-generation scene system. BSN is a better foundation for widgets than the old spawn-function approach: it reduces boilerplate, lets you compose widgets together, parameterize widgets with SceneComponent props, reference font/image assets, and register observers in the same declaration."

https://bevy.org/news/bevy-0-19/