Originally i thought that was just a brave issue but apparently its not.
i was using discord as a PWA trough brave when trying to window share.
i was trying to do the same torough librewolf and i had the same problem. so i asked a friend to join me on google meet (yes i know its abomination but i needed to test it) so i ran it from google chrome. and the result was the same.
however when i shared my screen back on the Discord’s Brave PWA it sound came torugh (the FPS of the video sucked terribly tough)
Conclusion: no matter what service or what browser i am using. window sharing Do not stream audio.
but at list on Brave audio come torugh. when i share the screen.
so anybody knows how to solve it? this is the one thing that keep me from exclusively using discord as a PWA. I am using windows 10 home edition 64 bit