so I have a scene with a cube map lighting and the reflections show nicely on the floor, however there seem to be no reflections at all coming from other objects in the scene - some are just 10 cm above very reflective floor.
How does reflectivity work in Playcanvas?
That’s the correct behavior all materials will reflect whatever are the contents of the cubemap.
For dynamic reflections of other objects, you setup box reflections in your project. Check how this engine example works:
If you are only looking for reflections on planar reflections, this example can be of help too: