Jenkins is the most popular CI/CD tool, which is completely open-source.

In Jenkins, a user can set up a notification when a Jenkins job fails/passes

There are many ways in which a user can notified when a Jenkins job triggers.

The most popular notification options are: 1. Slack 2. Email 3. pagerduty

Slack is the recent and most popular way to get notified for Jenkins job.  A user needs to install a slack notification plugin to send slack alerts.

Mailer plugin and SMTP has to be configured to send an email notification.

The Pagerduty Jenkins plugin will create a pagerduty alert and the user can extend it to create a PG ticket once the Jenkins job fails.