Below is an example of an ABAP report that uses the given SQL query to display an ALV report in SAP S/4HANA. Please note that in SAP S/4HANA, it is recommended to use Core Data Services (CDS) views and ABAP Managed Database Procedures (AMDP) for better performance and integration with the HANA database, but for the traditional ABAP approach, the following program can be used:

REPORT z_alv_sql_query.

TABLES: vbrp, vbrk.

PARAMETERS: p_start TYPE vbrk-fkdat OBLIGATORY,
            p_end   TYPE vbrk-fkdat OBLIGATORY,
            p_thres TYPE i OBLIGATORY.

TYPES: BEGIN OF ty_vbrp,
         vbeln     TYPE vbrp-vbeln,
         itemcount TYPE i,
       END OF ty_vbrp.

DATA: it_vbrp TYPE TABLE OF ty_vbrp,
      wa_vbrp TYPE ty_vbrp.

DATA: o_alv TYPE REF TO cl_salv_table.

START-OF-SELECTION.
  SELECT vbrp~vbeln, COUNT( DISTINCT posnr ) AS itemcount
    FROM vbrp
    INNER JOIN vbrk
    ON vbrp~vbeln = vbrk~vbeln
    WHERE vbrk~fkdat BETWEEN @p_start AND @p_end
    GROUP BY vbrp~vbeln
    HAVING COUNT( DISTINCT posnr ) > @p_thres
    ORDER BY itemcount DESCENDING
    INTO CORRESPONDING FIELDS OF TABLE it_vbrp.

  IF it_vbrp IS NOT INITIAL.
    TRY.
        cl_salv_table=>factory(
          IMPORTING
            r_salv_table = o_alv
          CHANGING
            t_table      = it_vbrp ).

      o_alv->display( ).
    CATCH cx_salv_msg.
      MESSAGE 'Error while creating ALV report' TYPE 'E'.
    ENDTRY.
  ELSE.
    MESSAGE 'No data found for the selected criteria' TYPE 'I'.
  ENDIF.

This program first defines parameters for the selection screen to capture the start and end date of the report period (p_start, p_end) and the threshold for the number of items (p_thres). It then performs a SELECT query using the provided SQL within the START-OF-SELECTION event. The result is stored in an internal table it_vbrp.

The program uses the class cl_salv_table to generate an ALV grid instance and display the data from the internal table. If no data is found or there is an error in creating the ALV display, it will output a message accordingly.

When adapting this program to your system, make sure that the types and field names correspond to the ones in your database and that the authorization for SQL queries and ALV display is granted accordingly.

Certainly, in the ABAP Open SQL statements in a SAP S/4HANA environment, variables must be preceded by the escape character @ to be correctly interpreted as host variables. Below is the revised program with the necessary corrections:

REPORT z_alv_sql_query.

TABLES: vbrp, vbrk.

PARAMETERS: p_start TYPE vbrk-fkdat OBLIGATORY,
            p_end   TYPE vbrk-fkdat OBLIGATORY,
            p_thres TYPE i OBLIGATORY.

TYPES: BEGIN OF ty_vbrp,
         vbeln     TYPE vbrp-vbeln,
         itemcount TYPE i,
       END OF ty_vbrp.

DATA: it_vbrp TYPE TABLE OF ty_vbrp,
      wa_vbrp TYPE ty_vbrp.

DATA: o_alv TYPE REF TO cl_salv_table.

START-OF-SELECTION.
  SELECT vbrp~vbeln, COUNT( DISTINCT posnr ) AS itemcount
    FROM vbrp
    INNER JOIN vbrk ON vbrp~vbeln = vbrk~vbeln
    WHERE vbrk~fkdat BETWEEN @p_start AND @p_end
    GROUP BY vbrp~vbeln
    HAVING COUNT( DISTINCT posnr ) > @p_thres
    ORDER BY itemcount DESCENDING
    INTO TABLE @it_vbrp.

  IF it_vbrp IS NOT INITIAL.
    TRY.
        cl_salv_table=>factory(
          IMPORTING
            r_salv_table = o_alv
          CHANGING
            t_table      = it_vbrp ).

      o_alv->display( ).
    CATCH cx_salv_msg.
      MESSAGE 'Error while creating ALV report' TYPE 'E'.
    ENDTRY.
  ELSE.
    MESSAGE 'No data found for the selected criteria' TYPE 'I'.
  ENDIF.

Notice the use of the @ symbol in the SELECT statement before the variables p_start, p_end, and p_thres, as well as before it_vbrp in the INTO TABLE clause. This ensures that the new Open SQL syntax in ABAP is adhered to.