HP insists you must use their cloud printing service, covers USB port with sticker

Well if you have an M234dw, then too bad: If it's already in 'self-bricked' mode then simply uncovering and trying to use the USB port will just make the motor spin up for half of a second and then just cancel itself. Nothing un-bricks the self-brick.

It will only ever be able to print testpages for the rest of its existence.