Couple more comments, might help..

In the Viewport, the instanced objects do obscure the 3D grid (but, nothing else);
If you enable "Wireframe" in the Viewport Display of the orignal instanced object, you can at least see the object's instances (while waiting for the bugfix)

OK. Maybe not so much a bug, more a change to adapt to the Collections = Groups scheme....

1. Open Blender and switch to the 3D viewport and the cycles render engine.
2. Delete everything in the viewport.
3. Add a plane.
4. Add a cube and scale it down (E.G. x0.1)

Move (M) the cube to a new collection
Right-click on the new collection and select "Instance to Scene"

1. In the object properties panel for the new "instanced" collection under relations, set the plane as it's parent.
2. In the object properties panel for the plane under instancing, select "verts".
3. Add a light object to the scene so you can see shading on objects in the scene.
4. Enter rendered viewport mode and notice that the plane and the instanced cubes are now visible. (Same applies for final renders)

@brett baker (roland): In a new scene that might work, but in my existing scene not. I can confirm this bug. I deleted my duplicated object (icosphere with emission material) and recreated it. Does not work.

EEVEE renders scene fine, cycles does not.