Within the MUX a channel has been created to display specific information from the Classic UI that isn't available in the MUX.
Within the page the "Save and Return" and "Return" buttons are displaying, which, when clicked, bring the channel into other aspects of the Classic UI. Is it possible to avoid this?
Clarity - Any
This is working as expected. A channel is displaying the desired webpage within a frame, it's not directly interacting with the content of the frame. Since the buttons display when viewing the Classic UI directly, they will also display when viewing within a frame.
To prevent the buttons from displaying the Classic UI theme would have to be customized to hide the buttons.