What is the output language from a cron job?
In my Spanish installation, I see lines as
Execute scheduled task: Enviar notificaciones de ingreso fallido (core\task\send_failed_login_notifications_task)
... started 22:22:01. Current memory use 20.2MB.
... used 0 dbqueries
... used 1.0994415283203E-5 seconds
Scheduled task complete: Enviar notificaciones de ingreso fallido (core\task\send_failed_login_notifications_task)
If it is only the admin user who sees English, then you log in as admin, go to your dashboard - preferences - preferred language - change English into Portuguese.