Reports

isOdd = new BehaviorSubject(false);

private _destoyed = new Subject<void>()

ngOnInit(): void {
 this.nestedFc.valueChanges
      .pipe(
        takeUntil(this_destroyed),
        map((value: any) => value % 2 !== 0)
      )
      .subscribe((odd) => {
        this.isOdd.next(odd);
      });

Front :

<span *ngIf="(isOdd | async) as value"> {{value}}</span>`

Dont forget to next into complete _destroyed on ngDestroy.

cdr.detectChanges() isn't best way to fix this.

And with this behaviorSubject impl, you can add this one (Optional but better perf) :

changeDetection: ChangeDetectionStrategy.OnPush,

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