Can’t recall that this has been as bad as in the current build.
Raytracing is completely hogging the entire computer for the time of the render (and, btw, it starts from scratch for any viewport capture).
Computer becomes sluggish, almost unusable, until render finishes.
Rhino 6 (6.23.20055.11282, 2020-02-24)
AMD Radeon Pro Vega 48 (8GB)