Controlling settings, permissions, and membership within Teams and channels
Thank you for that information.
As per below thread, once you make a channel private you cant revert back to public.
I am sharing the thread below and you might want to browse and find some suggestions from other users as helpful:
https://techcommunity.microsoft.com/t5/microsof...
You may also participate in the uservoice about this on below link:
https://microsoftteams.uservoice.com/forums/555...
Hope this helps.
Thank you.