Hi LElliott_RAND, welcome to the community.
That is really more of an individual attendee computer issue. When an attendee connects a headset to their computer either by USB or a traditional 1/8 jack, their computer should automatically switch to using that audio output.
For example, on my personal Windows 10 PC, I was an attendee in a webinar and dialed into the audio using my telephone. The organizer played a YouTube video using the video share feature and the audio played through my PC speakers. When I connected my USB headset the video audio switched to the headset and the GoToWebinar software gave me the option of switching from telephone to computer audio for the webinar. When I disconnected the USB headset the video audio went back to my PC speakers until I plugged in my regular headphones with a 1/8 jack, at which point the audio was then playing through those headphones.