hi,
NDI is one solution but generally need 2 screens, or even better 2 computers.
if you want to use the same computer, you can also use a web input, as long as the meeting solution you use can be reached by a web browser. I did this last week with a starleaf meeting, works fine.

Not exactly true. From the help files:

Window Capture Method

Select the method used to capture individual Windows.
GDI: This will work on the vast majority of systems with the exception of Windows Store apps and browsers such as FireFox and Chrome.

WindowsGraphicsCapture: This is available on Windows 10 1809 or higher and captures most applications including browsers and Windows Store apps.

DWM: This is available on earlier versions of Windows 10 and Windows 7 and can capture the same windows as GDI but with slightly lower CPU/GPU resource usage.

**************************************

Experiment with these and you will see that you can capture windows that are hidden.