Sadly no. It is on my list! So much to do, so little time. Not sure if I will get to it by 4.19.
I tested an upgrade to latest Embree (2.7 -> 2.17). Performance was nearly the same, so I reverted the upgrade. It’s not worth the careful regression testing we would have to do, for the same build times. Many of the recent Embree performance improvements only affect special types of rays which are not in heavy use by Lightmass. If our Embree usage changes, or a new Embree version comes out with improved performance, we will re-evaluate the upgrade.