Change the upload directory of Advanced Custom Fields file upload field.

acf-change-file-upload-directory.php

<?php
// ACF upload prefilter
function gist_acf_upload_dir_prefilter($errors, $file, $field) {
    
    // Only allow editors and admins, change capability as you see fit
    if( !current_user_can('edit_pages') ) {
        $errors[] = 'Only Editors and Administrators may upload attachments';
    }
    
    // This filter changes directory just for item being uploaded
    add_filter('upload_dir', 'gist_acf_upload_dir');
    
}

// ACF hook, set to field key of your file upload field
add_filter('acf/upload_prefilter/key=field_580ac5acd5616', 'gist_acf_upload_dir_prefilter');

// Custom upload directory
function gist_acf_upload_dir($param) {
    
    // Set to whatever directory you want the ACF file field to upload to
    $custom_dir = '/uploads/custom_dir';
    $param['path'] = WP_CONTENT_DIR . $custom_dir;
    $param['url'] = WP_CONTENT_URL . $custom_dir;

    return $param;
    
}