app.component.html

<form #myForm="ngForm" (ngSubmit)="onSubmit()">
  <div ngModelGroup="user">
    <label>
      Name:
      <input type="text" name="name" [(ngModel)]="name" required>
    </label>
    <div *ngIf="myForm.controls['user']?.controls['name'].invalid && myForm.controls['user']?.controls['name'].touched">
      <div *ngIf="myForm.controls['user']?.controls['name'].errors.required">Name is required</div>
    </div>
  </div>
  <button type="submit">Submit</button>
</form>