Channel folder cannot be deleted

My solution was by renaming the channels in Teams before deleting it. Then I was able to delete the folders from SharePoint.

I found a couple of workarounds by accident. Since we can't rename the folders in the Team's SharePoint document library, I deleted all the original channels and created new ones so the new file folders would match the channel names. (Obviously, this works best for brand new Teams) Then, to remove the original file folders, the first and best option I discovered is to select "Manage Access" from the file's actions menu.

This allows Team Owners to change a specific file to "Read Only" for Team Members, but also gave the option to "Stop sharing". By selecting this, Team Members will no longer see it in the Document Library on the SharePoint side, which is essentially the same as deleting it.

Finally, to hide the old folders for Team Owners, I created a new View called "Active Folders" and added a filter to only show items with a "Modified" date greater than the date that the original folders were created. Then I made that the Default View. But be careful because, not only does the filter applies to all the documents in the folders, but the default view gets applied to the Channel files tabs. (Again, this works best if you haven't actually started using the Teams site yet.)