Fieldset Legend Not Working in InDesign UXP

InDesign
1

image

Hi,
I’m trying to use a standard HTML and inside an InDesign UXP panel. My code looks like this:

  <legend>Do you agree?</legend>

    <input type="checkbox" id="chbx" name="agree" value="Yes!" />

   <label for="chbx">I agree</label>

However, the does not appear on the panel — the fieldset renders, but the legend line is not visible.

I’m wondering if this is expected in UXP, and whether I should use any Spectrum component instead to achieve a visible legend with proper styling.

Any guidance on the correct way to display fieldset-style grouping with a visible legend in InDesign UXP would be greatly appreciated.