Can u please explain what you want to override in that footer block ??,
As I have understood from your question -
if you want to change the file method's return type or arguments, please go by creating plugins for that class or preferences.
Or you can use the layout XML file in your module or theme by creating with the same name to over-ride that XML file ...
Ok, solved. Not the way I hoped, but the server we migrated from was using MariaDB and the new hosts were using MySQL. Switching it to MariaDB seemed to resolve the issues right away.
Hope this helps someone :)
Here is the code, for reference here, before return of collection we have just added complete category collection through Category Factory.
class ListProduct extends \Magento\Catalog\Block\Product\ListProduct