Abount handle custom element submit form

I have a custom form with html custom element, I tried to submit form, but it didn’t work.
My form is like this:

  <.form let={f} for={@changeset} phx-change="validate" phx-submit="save">
    <div class="form-group">
    <%= bx_label f, :slug %>
    <%= bx_text_input f, :slug %>
    <%= error_tag f, :slug %>
    </div>
    <div class="form-group">
    <%= bx_label f, :title %>
    <%= bx_text_input f, :title %>
    <%= error_tag f, :title %>
    </div>
    <div class="form-group">
    <%= bx_label f, :date %>
    <%= bx_date_select f, :date, format_pattern: "yyyy-MM-dd" %>
    <%= error_tag f, :date %>
    </div>
    <div class="form-group">
    <%= bx_label f, :author %>
    <%= bx_text_input f, :author %>
    <%= error_tag f, :author %>
    </div>
    <div class="form-group">
      <%= bx_label f, :content %>
      <ui5-tabcontainer class="full-width">
        <ui5-tab text="RAW">
          <ui5-label class="full-width">
            <%= bx_textarea f, :content, [rows: 50, class: "full-width", style: "width: 960px"] %>
            <%= error_tag f, :content %>
          </ui5-label>
        </ui5-tab>
        <ui5-tab text="Preview">
          <ui5-label class="full-width">
            <remark-element id="content-preview"><%= @blog.content |> raw %></remark-element>
            <script>
              const ipt = document.getElementById('blog_content');
              const pre = document.getElementById('content-preview');
              ipt.addEventListener('input', () => {
                pre.innerHTML = ipt.value;
                pre.requestUpdate();
                // pre.updated();
              });
            </script>
          </ui5-label>
        </ui5-tab>
      </ui5-tabcontainer>
    </div>
    <div class="form-group">
      <%= bx_submit "Save", phx_disable_with: "Saving...", id: "form-submit" %>
      <%= submit "Save", phx_disable_with: "Saving..." %>
    </div>
    <script>
var sb = document.getElementById('form-submit');
sb.addEventListener('click', (evt) => {
  console.log('form evt', evt.target);
  const find = (el) => {
    if (el.parentElement) {
      if (el.parentElement.tagName === 'FORM') {
        return el.parentElement;
      } else {
        return find(el.parentElement);
      }
    } else {
      return null;
    }
  }
  const f = find(evt.target);
  console.log('form el', f);
  f.addEventListener('submit', (evt) => {
    evt.preventDefault();
    return false;
  });
  // <%# f.submit(); %>
});
    </script>
  </.form>

Live view did not Intercept form submit event, is it a bug ?