Remove the Material Stepper header

@Simon K answer is correct. But it will affect all the stepper in your app. But if you want to use it for your specific component, use :host before the ::ng-deep. Then it will not affect other stepper (if any) in your application. For example of @Simon K' answer-

:host ::ng-deep .mat-horizontal-stepper-header-container {
  display: none !important;
}

You need to use a combination of ::ng-deep to get around shadow DOM and the !important flag to get around Materials own stylings:

::ng-deep .mat-horizontal-stepper-header-container {
  display: none !important;
}