TEC 3.0 Modify Custom Fields Output

// Many pieces of meta info pass through this filter, not only custom fields
add_filter('tribe_meta_factory_template', 'change_custom_fields', 20, 3);

function change_custom_fields($html, $label, $meta) {
    // We are only interested in one specific custom field
    if ('Custom Field Name' !== $label) return $html;

    // Swap out the current value for something else
    return str_replace($meta, 'My replacement text', $html);
}