Events from @ionic/angular package got removed from Ionic 5. You can see the breaking changes in Ionic5 here.

As it's mentioned in the breaking changes, you should use Observables.

For example, you can create the following service:

import {Injectable} from '@angular/core';
import {Subject} from 'rxjs';

@Injectable({
    providedIn: 'root'
})
export class GlobalFooService {

    private fooSubject = new Subject<any>();

    publishSomeData(data: any) {
        this.fooSubject.next(data);
    }

    getObservable(): Subject<any> {
        return this.fooSubject;
    }
}

Now, you can subscribe in any component like app.component.ts:

@Component({
    selector: 'app-root',
    templateUrl: 'app.component.html',
    styleUrls: ['app.component.scss']
})
export class AppComponent {

    constructor(private globalFooService: GlobalFooService) {
        this.initializeApp();
    }

    initializeApp() {
        // other code

        this.globalFooService.getObservable().subscribe((data) => {
            console.log('Data received', data);
        });
    }
}

Now, you just have to emit the event from some other component:

@Component({
    selector: 'app-home',
    templateUrl: 'home.page.html',
    styleUrls: ['home.page.scss']
})
export class HomePage {

    constructor(private globalFooService: GlobalFooService) {
    }

    onSomeButtonClick() {
        this.globalFooService.publishSomeData({
            foo: 'bar'
        });
    }
}

This is a very simple solution/example or alternative of the Events but you can tweak your code further to make it a namespaced event with a topic.

I have written a blog on this which can give you a full-featured solution so that with very less code change, you can upgrade your app.

https://medium.com/wizpanda/dealing-with-breaking-change-in-ionic-5-db3ba711dfcd

Events have been removed. You can do your own service as event as your own using observables,and subject behavior so you could publish to the ovserable and subscribe to get the value.