I am not sure if it is good user experience to have one filter always pre-selected by default. Can't use a toggle, because of the consistency issues with other pages. But I would like to keep all empty options hidden by default.
Another idea is to have a checkbox, by selecting it users will see hidden items. But there might be issues with responsive design, so I would prefer the first option.
Thank you.
No problem as long as it is clearly conveyed!
There is nothing wrong with having one filter by default selected as long as you make it very clear to the users that this filter is by default selected:
1- It should be clearly highlighted.
2- It would be best being the first option on the left. Neither the second nor the last but the first. This location helps users faster recognizes it, assuming it is Left to Right (LTR) language. It also mimics a drop-down filter with the first option selected.
