FormData won't pickup disabled form items and checkboxes don't have a readonly state

Consider a form which has a checkbox that the checked state is controlled by something else. Maybe a "Select/Deselect All" option. Here's a snippet where I've just hardcoded the value of the checkbox input.

<form>
  <label for="is-chicken">🐔?</label>
  <input name="is-chicken" type="checkbox" checked disabled />
  <button type="submit">Submit</button>
</form>

<script>
  const form = document.querySelector("form");

  form.onsubmit = (e) => {
    e.preventDefault();
    const formData = new FormData(e.currentTarget);
    const isChicken = formData.get("is-chicken");
    console.log(isChicken); // null
  };
</script>

I want to make sure that I can block the user from interacting with the checkbox and yet still read the value.

Maybe readonly would work?

<form>
  <label for="is-chicken">🐔?</label>
  <input name="is-chicken" type="checkbox" checked readonly />
  <button type="submit">Submit</button>
</form>

<script>
  const form = document.querySelector("form");

  form.onsubmit = (e) => {
    e.preventDefault();
    const formData = new FormData(e.currentTarget);
    const isChicken = formData.get("is-chicken");
    console.log(isChicken); // on
  };
</script>

MDN says

The readonly attribute is supported by  text, search, url, tel, email, password, date, month, week, time, datetime-local, and number<input> types and the <textarea> form control elements. If present on any of these input types and elements, the :read-only pseudo class will match. If the attribute is not included, the :read-write pseudo class will match.

The attribute is not supported or relevant to <select> or input types that are already not mutable, such as checkbox and radio or cannot, by definition, start with a value, such as the file  input type. range and color, as both have default values. It is also not supported on hidden as it can not be expected that a user to fill out a form that is hidden. Nor is it supported on any of the button types, including image.

When up against this set of requirements, maybe there's a better away to solve the problem.