Just trying out rhino6, been using 5 for years and objects are now vanishing from all viewports on both screens. I can still select them if I click where they should be and the properties shows them as they should be, just not visible. They seem to reappear for a time when exploded and joined, then vanish again. They seem to be objects created from a recent command, copy and paste from an inserted drawing, a boolean, create uv curves polylines etc. It doesnt look like your described video hardware and driver problems but here is what i’ve been using.