For non-raytracing, they introduced Thin-Translucency, as described here:
https://docs.unrealengine.com/en-US/…ncy/index.html
But that seem to not work with raytraced reflections. Or at least i was unable to get the described setup to work with raytraced reflections, but that could also just be a bug or a wrong setup on my end. Would be interested to see, if others get it to work with raytracing.