I'm running 3.1.1 on my home setup, Win11, and the Show Desktop button [X] (or shortcut D) is working fine if my default theme is a picture (or blank). If the default theme is a video background it is working fine until the video has reached its end and starts a new loop, then OpenLP theme takes over the screen again and i have to click Show desktop again.
Also it kills PowerPoint if it is open when you start OpenLP. Is this on purpose?