WORKING.html

    <ng-container *ngFor="let item of reverseStrings$ | async">
        <ng-container
        [ngTemplateOutlet]="string"
        [ngTemplateOutletContext]="item"
      ></ng-container>
       </ng-container>

working.ts

import { Subject } from 'rxjs';
import { map } from 'rxjs/operators';




  strings$ = new Subject<any[]>();

  reverseStrings$ = this.strings$.pipe(
    map(str => str.reverse())
  )
    
    
    
    
      this.strings$.next(newString);