Firefox Monitor
Firefox Monitor is a free and easy way to find out if your email address has been exposed to an online data breach since 2007. You can search for your email address from the web site at any time, or configure Firefox Monitor to send you alerts when your email is discovered to be part of a data breach. You will need a Firefox account to set up alerts.
According to the FAQs, Firefox uses Have I Been Pwned as the source database provider for their service. Their database is not totally comprehensive as it takes some time for some breaches to be discovered and they are not always given all the details of some breaches. If you don't want your email address to be searchable on Have I Been Pwned, they do provide an opt-out link.