Unfortunately not, the system reports false for canChangeOrientation on a Sidecar display:

    mac-utils  ./bin/RotateDisplay sidecar 0
    ID  UUID                                Can Change Orientation  Orientation Name
    1   37D8832A-2D66-02CA-B9F7-8F30A301B230    true                    0°          Built-in Liquid Retina XDR Display
    6   BF8D0007-9573-49E5-8130-75991ECB2F15    false                   0°          Sidecar
    4   FB46E28E-5B98-475A-A610-C15237238C8D    true                    0°          LG Ultra HD

    The display does not support changing orientation: Sidecar [ID: 6]