/*
 * FINAL REVISED SOLUTION
 * Keep the header as a grid and use grid properties to center the content.
 * Using !important on all rules to win any specificity conflict.
*/
.container-header {
  /* This is the key: Tell the GRID to center its child items */
  justify-content: center !important;

  /* Keep the display as grid, which the template expects */
  display: grid !important;

  /* Keep our background overrides */
  background: none !important;
  box-shadow: none !important;
}