I was trying out Blender Guru's Donut tutorial and got stuck while making the cup. The plane and the donut are not visible in the Layout tab even though the visibility is set. Everything is working fine in the Modelling tab and in the rendered image, so I'm sure it's a silly error which made this happen. I am not on Local view and I tried Alt + H, does not work. Blender version 2.92.0
The 3D Viewport has some own visiblity options if you bring up the sidebar with N, where you can disable visibility for certain collections. In the Layout View they are all disabled apart from the one that holds the camera and the light. The cup and saucer only show up there because they are not in one of those collections.
Disabling the Local Collections checkbox makes Blender ignore the Viewport settings for collections and shows them according to the settings in the Outliner. By default this setting is disabled so that the Viewport always uses the Outliner settings - I don't know why it's enabled in your scene.