I have animation packs I purchased for Unity that I would like to use in Unreal.  I had used this pipeline for Mixamo rigs and it worked.  It involved using timeline + fbx exporter in Unity to export the animations and then import into Unreal selecting the skeleton from the imported Mixamo mesh.

I did import a rigged model using AccuRig (Free) into Unreal without an issue.  I even was able to use a Mixamo animation on it.

With this model, I imported into Unity, selected Humanoid skeleton and used one of the animations from the pack and it worked.  When I used the same process to import and then attempted to import the animation using the Unread skeleton, it gave the following "Could not create a valid skeleton from the import data that matches the given Skeletal Mesh.  Check the bone names of both the Skeletal Mesh for this AnimSet and the animation data you are trying to import."

Regarding CC, it is possible to import an animation done this way and apply to a AcuuRig character and then export to Unreal?