On the later Mogs the front wings accomodate this shallow U bracket.
This is riveted onto underside top of wing, obviously in a blind fashion externally. The bracket appears to hold a captive nut allowing positive attachment of strut.
Richard
2018 Roadster 3.7 1966 Land Rover S2a 88 2024 Royal Enfield Guerrilla 450 1945 Guzzi Airone