<p>This is just for the demonstration purpose. In such case a better option would be the radio button grouped with the same name and value attribute.</p>
<details id="multiselect">
  <summary>Your favourite cars list</summary>
  <form>
    <fieldset>
      <legend>
        Cars
      </legend>
      <ul>
        <li>
          <label for="bmw">BMW</label>
          <input type="checkbox" id="bmw" name="car[]" value="bmw" />
        </li>
        <li>
          <label for="citroen">Citroen</label>
          <input type="checkbox" id="citroen" name="car[]" value="citroen" />
        </li>
        <li>
          <label for="skoda">Skoda</label>
          <input type="checkbox" id="skoda" name="car[]" value="skoda" />
        </li>
        <li>
          <label for="volvo">Volvo</label>
          <input type="checkbox" id="volvo" name="car[]" value="volvo" />
        </li>
      </ul>
    </fieldset>
  </form>

</details>

details {
  border: 1px solid #767676;
  border-radius: 3px;
  display: inline-flex;
  flex-direction: column;
  padding: 3px 6px;
}

details summary::marker {
  display: none;
  font-size: 0;
}

details summary::-webkit-details-marker {
  display: none;
  font-size: 0;
}

details summary::after {
  content: "\25BC" / "";
  display: inline-block;
  font-size: 0.6rem;
  height: 1rem;
  line-height: 1rem;
  margin-left: 0.5rem;
  position: relative;
  transition: transform 0.25s;
}

details[open] summary {
  margin-bottom: 1rem;
}

details[open] summary::after {
  top: -0.15rem;
  transform: rotate(180deg);
}

form {
  display: flex;
}

fieldset {
  border: 0;
  padding: 0;
}

fieldset legend {
  position: absolute !important;
  width: 1px !important;
  height: 1px !important;
  padding: 0 !important;
  margin: -1px !important;
  overflow: hidden !important;
  clip: rect(0, 0, 0, 0) !important;
  white-space: nowrap !important;
  border: 0 !important;
}

ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

ul li {
  border-radius: 3px;
  margin: 0;
  padding: 4px 2px;
}

ul li:hover {
  background: #eee;
}

ul li label {
  display: inline-block;
  width: 8rem;
}

const multiselectElement = document.querySelector('#multiselect');

const handleEscape = (event) => {
  const eventTarget = event.target;
  let key;

  if (typeof Object.getOwnPropertyDescriptor(KeyboardEvent.prototype, 'code') === 'object') {
    key = event.key;
  } else if (typeof Object.getOwnPropertyDescriptor(KeyboardEvent.prototype, 'key') === 'object') {
    key = event.key;
  }

  if (key !== 'Escape') {
    return;
  }

  const detailsElement = eventTarget.closest('details');

  detailsElement.removeAttribute('open');
  detailsElement.querySelector('summary').focus();
};

multiselectElement.addEventListener('keydown', handleEscape);

const allowOnlyOneCheckbox = (event) => {
  const eventTarget = event.target;

  if (eventTarget.nodeName.toLowerCase() !== 'input') {
    return;
  }

  const allCheckboxes = eventTarget.form.querySelectorAll('input');

  Array.from(allCheckboxes).forEach((inputElement) => {
    inputElement.checked = false;
  });

  eventTarget.checked = true;
};

multiselectElement.addEventListener('change', allowOnlyOneCheckbox);

External CSS

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External JavaScript

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