Is there an easy way to convert a world-space trace on an object into UV space?

Use FindCollisionUV node.

You can use a Line Trace hit result to find the UV that was hit. But make sure to do the following:

  1. Under Project Settings > Engine > Physics > Optimization, enable “Support UV From Hit Results”. This enables the feature but uses more CPU to store the UV information.
  2. When performing the Line Trace, ensure, “Trace Complex” is checked.