When I duplicate an artboard I would expect it to appear to the right of the selected art board or choose the next available space on the canvas. However this is not what always happens and instead the duplicate art board appears separated in a fixed position towards the right of the whole canvas until it runs out space.
When the artboards have reached the far right edge, Illustrator refuses to make any further artboards as it tells me the new one would extend beyond the canvas. The expected behaviour would be for it to find the next available space on the next row down as it does on desktop. I am forced to moved artboards from where Illustrator positioned them in order to make space for it to put more in that position it insists upon.