User Configuration > Administrative Templates > Microsoft PowerPoint 2016 > PowerPoint Options > General
User
HKCU\software\policies\microsoft\office\16.0\powerpoint
This policy setting controls whether users can turn on Live Subtitles during a presentation. By default, Live Subtitles are off but can be turned on by users. If you enable this policy setting, users can't turn on Live Subtitles during a presentation. If you disable or don't configure this policy setting, users can turn on Live Subtitles. Note: This policy setting only applies to subscription versions of Office, such as Microsoft 365 Apps for enterprise.