This question is for basic Firebase Analytics integration where a dependency is added and nothing else.
How does Firebase Analytics define Active User - does Firebase Analytics count active users as: foreground users as in users who actually opened the app OR background as well (for example if app has background process that runs daily without UI)?
An active user has engaged with an app in the device foreground, and has logged a user_engagement event.
The documentation is here: https://support.google.com/firebase/answer/6317517#active-users