how to share entire screen in macos screensharing/facetime?

it seems to be limited to a window or multiple windows, but i'm trying to demonstrate something to a remote user that involves dragging something from my desktop into a safari window. in the past i could share one of my 3 screens (and not all 3 of them at once), but now i hafta resort to Zoom or another solution, for something that macos used to be capable of.. am i missing something?