I set my audio output to my Bluetooth headphones and while there is sound output to my headphones it is also coming from the tv speakers at the same time. Can’t figure out why. Tried both my fancy cans and my AirPods, same issue. Changing the volume only affects the headphones so I can’t mute the tv speakers at all.
accessibility > multi audio output > connect Bluetooth headphones
then select TV audio and turn it all the way down. The select the headphones you want. Volume buttons should control headphone audio only, while tv is still turned down all the way.