Updating the status to “Try this instead” and have added the clarification that after 30 days the name is once again available.
The reason for this decision was that Channels can be restored 30 days after being deleted. During this time, we intentionally don’t support creating a channel with the same name. After the 30 days, the name is available.
You can workaround this by restoring a deleted channel, renaming it, and then deleting the channel again. The previous name is then available for use.
This workaround has already been mentioned in the comments and if an immediate reuse of a Channel Name is required, this is the recommended solution.
-WarrenLászló Szönyi commented
Sorry, but this is a mess. I have deleted a channel long time ago and the channel name is blocked since then. Cannot restore it either. Furthermore, renaming a Channel does not rename the Folder under SharePoint. So in case I want to reorganize the Channels (e.g. by adding some numbers to each) the directories under SharePoint will not follow the structure. In case I want to reorganize the directories under SharePoint (e.g. by adding some numbers to each) Teams will not show my documents anymore as the Channels are linked to SharePoint Folders by their old names.
PLEASE do not block names for which no Channels in Teams and no Folders in SharePoint exist anymore.
PLEASE provide us the option to update the link of Channels to SharePoint Folders manually under Channel Management in Teams. Teams should list all existing SharePoint Folders of a specific Team and the admin should be able to manually repair broken links (caused by renaming folders in SharePoint).
Thanks in advance.