di.xml

<!-- To generate Interceptor, declare a plugin for virtualType, but plugin won't be executed with this alone -->
<type name="\Magento\LayeredNavigation\Block\Navigation\Category">
    <plugin name="my-plugin" type="\MyVendor\MyModule\Plugin\BlockNavigation"/>
</type>

<!-- For plugin to be actually executed, declare the same plugin for actual class -->
<type name="\Magento\LayeredNavigation\Block\Navigation">
    <plugin name="my-plugin" type="\MyVendor\MyModule\Plugin\BlockNavigation"/>
</type>


<!-- This is virtualType declaration in vendor/magento/module-layered-navigation/etc/frontend/di.xml -->
<virtualType name="Magento\LayeredNavigation\Block\Navigation\Category" type="Magento\LayeredNavigation\Block\Navigation">
    <arguments>
        <argument name="filterList" xsi:type="object">categoryFilterList</argument>
    </arguments>
</virtualType>