New git 4.0-beta commits and 4.0-beta unitypackages are available for the latest Spine Editor version 4.0.27-beta (binary and json formats have been changed in this editor version).
When using this runtime and Spine Editor version your skeletons should all work as expected, without errors. If you encounter any problems, please let us know.
The unitypackages are available here as usual:
Spine Unity Download