We acknowledge the customer demand for Private Channels and have been hard at work on it. Private Channels is currently in preview with a select group of customers. We expect to release the feature to the public later this Fall, and will update here when we are starting to roll out to all customers. We appreciate all the feedback you have provided to us on this forum and thank you for your patience.
~AlexDavid Costar commented
Channel level security is a significant gap that limits the full usage of Teams. Having a Teams site for an enterprise-wide department is effective, but not being able to limit specific artifacts and sensitive information to a few within that department continues to be an issue.