@Rudy Martin you can't do this with filter but you can do it with search.
board:boardname label:x -label:y
would do what you described for cards on board "boardname".
You can save searches if you have Trello gold/business class, and recent searches you performed appear in mobile search history so as long as your requirements are consistent you can set this up and re-use the same searches over and over.
All the Trello search operators are here:
If you had to thrive a new habit during a lockdown, what would it be? Trello
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event