In an older post on his blog Mohammed Said, Laravel Employee #1, shares a cool trick on how to avoid having to create an event listener.

Instead of having to create a class for the listener and another for the notification/mailable, wouldn't it be cool if we can register the Notification/Mailable as an event listener? ... While some may consider this an anti-SRP hack I think it's a pretty neat implementation that you can use in your application to prevent creating an extra listener class, your call :)

https://themsaid.com/laravel-mailables-notfiications-as-event-listeners-20170516/