Upgrading from Unity 2018 LTS to 2019 LTS
Unity no longer supports importing multiple animations from a single .blend file. Exporting to an exchange format like .fbx is recommended instead, which is how the base game assets have always been handled. Note that this is recommended for meshes/models as well. Read more details on the Unity issue tracker here.
2018 LTS Availability
For archival purposes the 2018 LTS version of the game will remain in a “unity-2018” beta branch.