material_base-8.x-2.x-dev/themes/material_base_mdc/templates/form/input--submit--button.html.twig

{#
  Historically Drupal uses <input type="submit"> element for buttons.
  The modern way is to use <button> element because it allows putting
  nested markup and using advanced styling. For compatibility with
  contrib modules Material Base comes with <input> element by default.
  But if you want to have <button> element for buttons, copy this template
  to your custom theme and rename to `input--submit.html.twig`.

  Have to use full template path because button.html.twig is not defined
  in templates registry yet.
  
  See https://www.drupal.org/project/drupal/issues/1671190
#}
{% extends "@material_base_mdc/form/button.html.twig" %}