When transferring a character to UE (5.7) with clothing that has a texture in the OPACITY box (Texture Setting/PBR), the resulting material does not cast a shadow (for at least direct lighting). When using "Hide Mesh" with that clothing, the character's skin is removed during the transfer (Transfer File Settings "Delete Hidden Mesh" is ticked). This results in the character's shadow having places where there is no shadow. See the attached screenshot from a character in UE 5.7.

How to reproduce:
1) Load a clothed character into iClone 8
2) Choose a piece of clothing, and hide a portion of the character's mesh beneath the clothing
3) Go to Modify, then Material
4) Add a full white texture to OPACITY for the material. (Make sure there is only one material for the mesh.) This will force the AutoSetup to use "RL_Standard_Opacity" as the material's parent rather than the normal "RL_Standard" parent, which is needed for testing purposes.
5) Tick "Delete Hidden Faces" and export the mesh for UE5
6) Import the character into UE 5.7
6) Create a new open world level in UE5 (with terrain and sunlight) and add the character
7) Note that the material leaves no shadow, even though the material is completely visible.

When the Opacity of the PBR material has an assigned material (a mix of black and white), Auto Setup assigns "RL_Standard_Opacity" as the master material, rather than "RL_Standard."

"RL_Standard_Opacity" does not cast shadows for its material instances. See the attached image taken from UE 5.7.

The solution is actually easy. Editing "RL_Standard_Opacity", selecting the Result Node and ticking "Cast Ray Traced Shadows" seems to fix the problem. See the attached screenshot. However, I have not verified this for other cases.

This fix needs to be made and tested for the next release of Auto Setup. Otherwise, I have to edit each and every project's material; this is very time consuming.