fail to get parent category name

I have a category landing phtml, I want to add a this main category name there.
This page is main category page, under this main category page, it has few subcategory.
I would like to get the MAIN category name in this landing page. But I cannot retrieve it.

<?php
$viewModel = $block->getViewModel();
?>
<div class="category-landing-grid">
    <?php foreach ($viewModel->getSubcategories() as $category) : ?>
        <div class="category-landing-grid__item">
            <div class="category-landing-grid__item-wrapper">
                <a href="<?= $category->getUrl() ?>">
                    <span><?= $category->getName() ?></span>
                    <img src="<?= $viewModel->getCategoryImage($category) ?>" alt="<?= $category->getName() ?>"/>
                </a>
            </div>
        </div>
    <?php endforeach; ?>
</div>

I am success to get the page title, but I cannot get the category name.

model view:

public function getTitle()
{
    return $this->_pageTitle->getShort();
}

phtml file:

<?php
echo $viewModel->getTitle();
?>

How do I get the parent category name for the phtml file?

I did follow the instruction from some website, but not success
https://www.mageplaza.com/devdocs/how-get-current-product-category-magento-2.html#3-steps-to-get-current-product–current-category-in-magento-2

May be it cannot be use to get the category name of Parent category (current category landing page)?