結論structuredCloneを使う

const obj = {
  sample: "sample",
};
const obj2 = structuredClone(obj);

console.log(obj);
// { sample: "sample" }

console.log(obj2);
// { sample: "sample" }

obj.sample = "aiueo";
console.log(obj);
// { sample: "aiueo" }

console.log(obj2);
// { sample: "sample" }