They are grayed out for everyone else, so they can’t actually read the contents.

Caveat being if you move the window around really fast sometimes it’s possible to catch a glimpse.

Maybe that's changed, but a couple months ago we tested it on vanilla Ubuntu in the team at $dayjob and we could see everything. Nothing was grayed out.

Sounds like it works a little differently on Linux.

To be honest, I'm actually surprised and impressed that they support screen share in the Linux version because of how many different flavors of i.e. WM there are in the wild.

I don't believe that the WM would enter into it — as long as folks are using X11 the code should be, I think, the same for any WM or DE.

Now, using Wayland it may or may not be possible, depending on which WM/compositor/whatever you are running.

Zoom on Mac and/or windows seems to black out other windows if they appear on top of the target window. I've seen that happen a few times so definitely does happen, just perhaps not on Linux.

I literally quit all messaging apps when presenting to people for any period of time more than ~10s.

You could also disable notifications if your OS has that kind of feature. Mine does, so I took advantage of that after the first incident of being interrupted. It's a nice feature.

Let me introduce you to Microsoft Teams which comes with custom notifications ignoring do-not-disturb settings.

On windows?

Hm, I don't think that is the case for Gnome/GTK as pipe wire should grab the image before it's composed as far as I know.

But I can't check as I'm running sway which (I think, haven't checked for a while) doesn't yet support single window screen sharing.