Motion sensor sprinklers.
Put out pans of vinegar - they don't like the smell. They also don't like the smell of wet coffee grounds.
Some tips here: https://www.craftylittlegnome.com/keep-cats-out-of-the-flower-bed/
Cats dislike strong citrus smells, cayenne pepper sprinkled in the area, and Essential oil of Rue, or Rue plants.
Spraying them with water is also effective, but requires on going use of motion sprinklers, and your water bill...
If the cats are ferile, or belong to neighbors, you could call animal control. Most municipalities have laws against unleased pets, due to health hazards.