Chrome extension : testing if a tab is captured

Question

In a chrome extension, I'm trying to figure out if the user is currently sharing (presenting) its screen (full-screen or window or tab) to other people in a ZoomMeet/GoogleMeet/... when the extension is activated.

I tried to use getCapturedTabs() : https://developer.chrome.com/docs/extensions/reference/api/tabCapture#method-getCapturedTabs to no success ; the returned array is always empty (even when I share my screen before).

I also tried MediaDevices.getUserMedia() : https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getUserMedia which actually captures and returns my current tab but tells nothing about an already shared/captured one...

Does anyone have any idea how to achieve what I'm after ?