WebForm Term Reference Checkboxes

PHP8, any browser:

The webforms I have created can have attached Term Reference Fields, in order to list Vocabularies, however if those fields are set to Checkboxes or Radio, whether multiple or single value, they fail to display on site.

The reports log shows 'Theme hook "checkboxes" not found.'

I have tried Bootstrap Lite 5 and Basis themes, same results.

And I can see 

function bootstrap5_lite_checkbox($variables) {
  $variables['element']['#attributes']['class'][] = 'form-check-input';
  return theme_checkbox($variables);
}

in the bootstrap theme.

Of note, versions: Webform = 1.x-4.25.0

Webform Reference = 1.x-1.0.0