The client's contribution feed is a browser tab

Your agency produces webinars for clients who cannot install OBS and should not be asked to. The setup is a container: slides loaded, browser tabs staged, the display opened with ?decorations=false so the desktop is nothing but the content. The client opens that display URL in a tab and presents: clicking through their own deck on your machine.

Your side runs the show: ffmpeg capturing the display, one pipe path fanning the stream out to the audience's ?video URLs, and one extra receiver archiving the master copy for the client's site.

The client's technical requirement is "can open a link." Yours is one container you reset and reuse for every event.