minecraft_lzstools/data/lzstools/predicate/unbreaking/offhand/3.json

{
  "condition": "minecraft:entity_properties",
  "entity": "this",
  "predicate": {
    "equipment": {
      "offhand": {
        "predicates": {
          "minecraft:enchantments": [
            {
              "enchantment": "minecraft:unbreaking",
              "levels": 3
            }
          ]
        }
      }
    }
  }
}