The developer working on integrating network display functionality into GNOME Shell shared short video clip to the GNOME sub-reddit [...] the feature adds a “screencast” button to the row of actions in the Quick Settings menu. Clicking this opens a modal picker where the user can select any Miracast or Chromecast compatible displays on the network.
What speakers/ receiver system are you using? I'm still shopping that part as well. I'm trying some wifi speakers but haven't got them where they need to be yet.