DH just wondered what I was doing when I got up and microwaved a plate I had one of BILs square plates here so was able to test for you. We have a LG with a round cavity and the plate didnt spin...doesnt say what size it is so sorry not much help.
I do love the round cavity for ease of cleaning.
Just take a plate with you to test I did check if you could see if you would be able to tell if it wasnt turned on and you would.