I am trying to implement a reactive angular form where either A or B has to be entered. A is a unique id and B is a set of values which identify the id. Now I try to validate a Form that is valid if either A is entered or B is entered including all the required values. I found several solutions that implement this behavior based on FormFields but was not able to get it working with the group of values.

<form class="container" [formGroup]="myForm" (ngSubmit)="onSubmit()">
      <mat-form-field class="w-1/2">
        <mat-label>ID</mat-label>
        <input matInput type="number" formControlName="id">
      </mat-form-field>

      <div class="grid grid-cols-3 gap-4" formGroupName="innerGroup">
        <mat-form-field>
          <mat-label>First Name</mat-label>
          <input matInput type="number" formControlName="firstName">
        </mat-form-field>

        <mat-form-field>
          <mat-label>Last Name</mat-label>
          <input matInput type="number" formControlName="lastName">
        </mat-form-field>
      </div>
</form>

My first idea was to override the default validator for the form but I could not figure out how to do that. Not even sure if it would be possible. I was trying to adjust https://stackoverflow.com/a/48714721 to work in my scenario but I had no idea how to get it to work because of the additional complexity with the inner form group.