Scala 2.13.0-M5 further refines and polishes the new collections API, among other improvements. As of this milestone, 2.13 is now feature-frozen.
For details, see the release notes: https://github.com/scala/scala/releases/tag/v2.13.0-M5
Core libraries will appear in the coming days and weeks. Available libraries will be added to https://github.com/scala/make-release-notes/blob/2.13.x/projects-2.13.md