

They use XDG Desktop Portal, which makes video and audio capture system level instead of application level to enhance security. When a program wants to record your screen you get a pop up to choose which screen/window to share. After that the app can only see that window or screen.
Are you closing the spectacle window after taking a screenshot? I found that you need to keep it open for the image to stay in the clipboard. When I have the time I can check how I’ve set it up if that doesn’t work for you. Although I only copy to clipboard, not save as well.