Hello. In a studio with a big echo in which i send through speakers the audio from skype and the mic from the person in the studio catch this audio and bring in echo i used the vst3 audio plugin https://www.wtautomixer.com/ i insert it to every audio in source and it did the magic thing. Maybe it can work in your workflow

Right. I forgot to write that i send only the mic audio through an Audio Bus and from another one audio bus assigned to an audio device only the viewers audio in the studio but this not prevent the echo 100% if the audio from the viewers has to be loud in the studio and in my situation the plugin helped a lot