What this MDD-Export-Addon does is to create a “Shapekey” for every frame and name it after that frame as well as creating a “Keyframe” for activating each “Shapekey” only at that frame. After exporting the animation as MDD, you can delete the rig and the “Armature Modifier” on the deformed mesh and import the MDD file created before. It’s important to do it on the same mesh so that the “Vertex Count” fits:

