"Operation not permitted" for root when trying to ls or chmod -R /Users/user/Desktop

"user" can't do it either. Permission of Desktop/ is set to 700 and owned by "user". Here's the sderr output for ls -R command in the home directory:

ls: Desktop: Operation not permitted ls: AddressBook: Operation not permitted ls: CallHistoryDB: Operation not permitted ls: CallHistoryTransactions: Operation not permitted ls: com.apple.TCC: Operation not permitted ls: com.apple.sharedfilelist: Operation not permitted ls: CloudKit: Operation not permitted ls: com.apple.ap.adprivacyd: Operation not permitted ls: Calendars: Operation not permitted ls: com.apple.CloudDocs.MobileDocumentsFileProvider: Operation not permitted ls: com.apple.Home: Operation not permitted ls: com.apple.Safari: Operation not permitted ls: com.apple.news: Operation not permitted ls: Cookies: Operation not permitted ls: HomeKit: Operation not permitted ls: IdentityServices: Operation not permitted ls: Mail: Operation not permitted ls: Messages: Operation not permitted ls: CoreSpotlight: Operation not permitted ls: PersonalizationPortrait: Operation not permitted ls: Safari: Operation not permitted ls: Sharing: Operation not permitted ls: Suggestions: Operation not permitted

You need to add Terminal to the list of apps that have Full Disk Access in the Privacy pane of System Preferences > Security & Privacy.

Unlock the padlock in the bottom left, and drag the Terminal app icon onto the window.