Cannot complete Trailhead Create and Configure an External Client App because Require Proof Key for Coke Exchange (PKCE) extension for Support Authorization Flows is selected by default and cannot be deselected

Cannot complete Trailhead Create and Configure an External Client App because Require Proof Key for Coke Exchange (PKCE) extension for Support Authorization Flows is selected by default and cannot be deselected 

Note: I cannot deselect this, so I can't complete this trailhead.  Can someone from Support help me?  My Org ID is: 00Daj00000rQGdh