Enable the mono audio accessibility feature on the login screen.
This feature allows to switch the device mode from the default stereo audio to the mono audio.
If this policy is set to true, the mono audio will always be enabled on the login screen.
If this policy is set to false, the mono audio will always be disabled on the login screen.
If you set this policy, users cannot change or override it.
If this policy is left unset, the mono audio is disabled on the login screen initially but can be enabled by the user anytime.