To my knowledge it is not possible to add the channel calendar to Outlook.
As channel calendar is the filtered version of group calendar (by filtering the events within the channel).
You can however, add the group channel to Outlook. While note that it may show all events from all channels.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.