Blur or pixelate forground

Does anyone know how to blur or pixelate the foreground, or the whole image. My son uses zoom for school and has issues with people seeing him, he has been using it with the camera off, but teachers think he signs in and disappears, what we want to do is get him to use his camera, and be able to adjust the foreground or whole image blur enough that that it is apparent he is there, and is moving etc but that they can’t actually make out any detail. Ideally the adjustment should be adjustable. We have tried some chrome blur add-ins but they don’t seem to work with Zoom.