Any tips for finding companies that use a specific development technology?

Hi everyone! At the moment I am building an app called Ezfire that is a developer tool for companies using Firebase and Google Cloud Platform that lets users write and execute database queries for Cloud Firestore. At the moment I am trying to find my first customer for this app and start growing the user base.

Although I know there are a lot of companies using this technology, I'm having difficult building a large list of companies because company tech stacks aren't always publically available.

Do you have any tips for how to find companies that are using a specific technology?