I am jotting down what I am sure are a few obvious notions about object in art.
Objects moved from being seen as the elements depicted in the artwork to the physical work of art itself to including the artist and/or viewer to being summarily elements installed in a presentation space, which works of solid art always have been, whether specifically viewed that way or not. Objects change a space.
With a video in a monitor, the monitor comes across as a primary object, just as a stretched canvas comes across as a primary object. It's hard for me to view the video shown within the monitor as an object. However, within the duration of projection, I can view a projection not contained within a physical object (or projected onto a shaped physical support), as an object, even if it is less materially solid, because no physical support detracts from it as an element in the presentation space.