How to make select filter work with http calls dynamically?

I got it working to fill the select options dynamically but the search isn't working.And how to add a data-additional attribute to set from additionalData key?

My component class:

export class AppComponent implements OnInit {
  searchText = new Subject();
  filteredOptions: Observable<any[]>;
  options = [];

  constructor(private appService: AppService) { }

  ngOnInit() {
    this.appService.getJson()
      .subscribe((data: any) => {
        this.options = data.options.map((option : any) => {
          return {
            value: option.id,
            label: option.name,
            additionalData: option.additionalData.join(',')
          }
        });

        this.filteredOptions = this.searchText.pipe(
          startWith(''),
          map((value: string) => this.filter(value, this.options))
        );
      });
  }

  filter(value: string, options: any[]): any[] {
    const filterValue = value.toLowerCase();
    return options.filter((option: any) => {
      console.log(option, filterValue);
      return option.value.toLowerCase().includes(filterValue) || option.label.toLowerCase().includes(filterValue);
    });
  }
}

HTML:

<div class="md-form">
  <mdb-select-2 placeholder="Choose your option" label="Example label">
    <mdb-select-filter
      [ngModel]="searchText | async"
      (ngModelChange)="searchText.next($event)">
    </mdb-select-filter>
    <mdb-select-option *ngFor="let option of filteredOptions | async" [value]="option">{{ option.label }}</mdb-select-option>
  </mdb-select-2>
</div>

I don't get why the filter isn't working. It's nearly the same like in this autocomplete example: https://mdbootstrap.com/docs/angular/forms/autocomplete/#remoteData

I can see the console log output only once (on init) and not again when typing anything in the search/filter field.

EDIT: demo application: https://github.com/dtrunk90/mdb-select-filter-http You either need to add a SSH key to GitLab or change the SSH-based URL to the HTTPS based URL in package.json.