Hello, There was a similar problem with the macOS platform. Got a response from Apple tech support. "You can delete a platform if a build has never been uploaded for the platform you wish to delete. Additionally, at least one existing platform version needs to be in an editable app status. If the criteria is met, hover over the platform you wish to delete and click the delete button (–) that appears to the right of the platform." The problem was solved in this way. But it is important that you have Admin or Account Owner rights.