I took a closer look at the problem and it seems that routerOutlet always fetches the next parent instance of ion-router-outlet from the respective page. So if we call routerOutlet.canGoBack() inside app.component.ts, the value would always be false because ion-tabs have their own ion-router-outlet.

Thats why using this.routerOutlet.canGoBack() inside childpages of ion-tabs will return the correct boolean value.

If you need to handle something globally (like using android hardware backbutton to exit app) you can use following snippet:

@ViewChild(IonTabs, { static: true }) private ionTabs: IonTabs;
...
constructor(
  private platform: Platform,
) {
  this.platform.backButton.subscribeWithPriority(-1, () => {
    if (!this.ionTabs.outlet.canGoBack()) {
      App.exitApp();
    }
  });
}

It’s important that you handle the logic inside tabs.page.ts since we use the Viewchild of ion-tabs, which contains the outlet for tabbed pages.