Hey,
I am posting this as a PSA as I just spent a good couple hours after switching to UDynamicMeshComponent wondering why my complex collision wasn’t working anymore.
The short answer is that the UDynamicMeshComponent has a maximum triangle limit for generating complex collisions and if you go above that it will not generate complex collision for you.
You can find it with the cvar geometry.DynamicMesh.MaxComplexCollisionTriCount and it defaults to 250,000 tris.