If it is a standard 2x4 or 4x4 blank wall plate to cover installed electronics, then it should not be a problem as long as the edges and corners are not sharp. However, it is the TSA and one never knows. As soon as I can predict the TSA with accuracy, I'll start day trading.

If you are checking a bag, remove the plate and throw it in the bag.

You may be able to minimize scrutiny a bit by taping the edges.

I know this sounds silly, but take a bit of plywood, cut a hole like in a wall, and mount the unit on the plywood, they will likely never think of the possibility that it could be taken apart and it will look like the wall plate that it is.

Of course, YMMV.