Magento – Magento 2 – show product attribute labels

The method getAttributeText looks like this:

public function getAttributeText($attributeCode)
{
    return $this->getResource()
        ->getAttribute($attributeCode)
            ->getSource()
                ->getOptionText($this->getData($attributeCode));
}

Notice the last 2 lines.
They mean that the method calls getOptionText from the source model class.
I see that your attribute has a custom source model npm_recurrex/package_source. Make sure that model has the method getOptionText or it's parent class has it and returns what your need.

[EDIT]
Your getOptionText is wrong.
It would work if the attribute would be of type select.
But it doesn't work for multiselects.
Here is a scenario. Actually I'm using your scenario.
$_product->getData('package') returns 1,2.
And I assume your options are something like this:

$options[] => array('value' => 1, 'label'=>'Option 1');
$options[] => array('value' => 2, 'label'=>'Option 2');
$options[] => array('value' => 3, 'label'=>'Option 3');
$options[] => array('value' => 4, 'label'=>'Option 4'); 

In this case, your method receives as parameter 1,2 and you check if there is an element in $options with value = 1,2. and there isn't.
Try to make your method look like this:

public function getOptionText($value)
{
    $options = $this->getAllOptions(false);
    $optionsByValue = array();
    foreach ($options as $item) {
        $optionsByValue[$item['value']] = $item['label'];
    }

    $values = explode(',', $value);
    $returnValue = array();
    foreach ($values as $_value) {
         if (isset($optionsByValue[$_value])) {
             $returnValue[] = $optionsByValue[$_value];
         }
    }
    return implode(', ', $returnValue);
}

Untested code so look out for typos.

You can set the frontend labels with the following code in your UpgradeData or InstallData script:

    /** @var \Magento\Eav\Setup\EavSetup $eavSetup */
    $eavSetup = $this->eavSetupFactory->create(['setup' => $setup]);

    $attribute = $this->productAttributeRepository->get($attributeCode);
    $sourceModel = $attribute->getSourceModel();
    $frontendLabels = [
        $this->attributeFrontendLabelFactory->create()
            ->setStoreId(1)
            ->setLabel('Label 1'),
        $this->attributeFrontendLabelFactory->create()
            ->setStoreId(2)
            ->setLabel('Label 2'),
    ];
    $attribute->setFrontendLabels($frontendLabels);
    $this->productAttributeRepository->save($attribute);

    if ($sourceModel !== null) {
        $eavSetup->updateAttribute(
            \Magento\Catalog\Model\Product::ENTITY,
            $attributeCode,
            \Magento\Catalog\Api\Data\EavAttributeInterface::SOURCE_MODEL,
            $sourceModel
        ); // this is needed as the attribute repository throws away the source model while saving in Magento 2.2.5
    }

$this->eavSetupFactory is of type \Magento\Eav\Setup\EavSetupFactory.

$this->productAttributeRepository is of type \Magento\Catalog\Api\ProductAttributeRepositoryInterface.

$this->attributeFrontendLabelFactory is of type \Magento\Eav\Api\Data\AttributeFrontendLabelInterfaceFactory.

You should inject them via Dependency Injection in the constructor.