This is still being worked upon. I hope to have more details in the next couple months.
Please know the team is actively working on this feature.
Hi Everyone – thank you for your patience. As was commented by someone below, Suphatra is no longer at Microsoft, but rest assured we are working on this feature.
~ AlexAnonymous commented
Just spent the last couple hours trying to figure out how to restrict Guests from specific channels, glad its being worked on, thanks. Agree completely with the above selections.
Still in the works, no additional details are available yet.