Google meet and slack have the same issue with multimonitor setups. It works great with a single monitor but not multiple. This is not just Wayland but X as wel

Google meet and slack have the same issue with multimonitor setups. It works great with a single monitor but not multiple. This is not just Wayland but X as well. You can cheat it by starting the session with a single monitor activated, xrandr-ing the other one active after you start sharing, but that shouldn't be required. The single screen sharing application I've had success with on Linux+XOrg and multimonitor is Zoom. No other application properly allows me to share just one screen.