After Upgrading to Magento 2.4.3 the pagination is not working anymore

Your concept is slightly lacking. The query should be at least moved outside of the template into Block class.

Then in the same class you can add something like this to solve your pagination issue:

protected function _beforeToHtml()
{
    $blockName = $this->getToolbarBlockName();
    if (!$blockName) {
        $blockName = 'product_list_toolbar';
        $this->setToolbarBlockName($blockName);
        $this->getLayout()->createBlock(
            $this->_defaultToolbarBlock,
            $blockName,
            array(
                 'show_toolbar' => $this->getData('show_toolbar'),
                 'list_mode' => $this->getData('list_mode'),
                 '_current_limit' => $this->getData('limit')
            ))
            ->setChild(
                $blockName . '_pager',
                $this->getLayout()->createBlock('page/html_pager', $blockName . '_pager')
            );
    }

    return parent::_beforeToHtml();
}

Unless you make fun of reinventing the wheel you can also use this extension to create a listing of all products of your store along with couple of other useful listings:

https://github.com/tim-bezhashvyly/CustomListing

Adding ?p=2 to the end of your url works fine, so that shows us that the pagination is active, it's just the block not displaying.

Infinite scroll extensions typically 'click' the pagination in the background, hence that one not working for you

Do you have this code in list.phtml?

<div class="toolbar-bottom">
    <?php echo $this->getToolbarHtml() ?>
</div>

Also, check settings such as 'is anchor' in the category settings in Magento admin - there's a chance you're targeting the wrong catalog_category handle in your catalog.xml.