How to fix "Error filtering template: Bucket does not exist" in Magento 2?

You should know that this is a common issue with Magento 2.2. After the update, the Root category is not anchored, even if set to "Yes".
So you can go ahead and switch it off and then on again (Save!) and it should resolve the issue.

And to improve the process of searching products in your store, you can use the Layered Navigation Lite extension. With it, you will be able to add various filters to your store and speed up the shopping process while making your store more user-friendly.