I'm creating pendant lights for viewing in in AR Quick Look, is it possible to anchor these to the ceiling of a room?
Yes this is something that is supported in AR Quick Look. You can place objects on the ceiling by dragging them there. This can be done using a regular horizontal (or vertical) anchor.
However, there are potential challenges to be aware, the biggest is that ceilings usually lack a lot of feature points, which makes it difficult to detect a proper plane. Using a device with LiDAR can improve the results that you get.