If you do the retargeting of the skeletons you can replace the skeleton reference inside the AnimBP
If you do that you can then use the skeletal mesh, because the AnimBP will become compatible with that Skeletal mesh.
Mind you, if the proportions between your character and the marketplace character are the same, the animation will play without any issues, but if the proportions are way off, you’ll see weird behaviourduring the animations, because of the difference between the skeletons.