New version:

I solve this using a PopoverController inside my modal component:

// template
<ion-item>
  <ion-label position="floating" color="primary">A partir</ion-label>
  <ion-input
    formControlName="timeStarts"
    (ionFocus)="presentTimeStartsPicker()"
  ></ion-input>
</ion-item>

// component
async presentTimeStartsPicker() {
  const popover = await this.popoverController.create({
    component: IonDatetime,
  });

  await popover.present();

  popover.firstChild.addEventListener('ionChange', (e: Event) => {
    this.filterForm.patchValue({ timeStarts: e.timeStamp });
  });
}

Old version:

I solve this using a PopoverController inside my modal component with a small component to render the IonDateTime.

// template
<ion-item>
  <ion-label position="floating" color="primary">A partir</ion-label>
  <ion-input
    formControlName="timeStarts"
    (ionFocus)="presentTimeStartsPicker()"
  ></ion-input>
</ion-item>

// component
async presentTimeStartsPicker() {
  const popover = await this.popoverController.create({
    component: TimePickerComponent,
    componentProps: {
      ionChange: (e: Event) => {
        this.filterForm.patchValue({ timeStarts: e.timeStamp });
      },
    },
  });
  await popover.present();
}

...

@Component({
  selector: 'app-popover-datepicker',
  template: `<ion-datetime (ionChange)="onChange($event)"></ion-datetime>`,
})
export class TimePickerComponent {
  @Input() ionChange: (e: Event) => void;

  onChange = (e: Event) => this.ionChange(e);
}