It's harder than expected

  1. setup SMTP server in controller -> Mail Server, get a test email working and all that
  2. enable emails in the site settings
  3. enable emails in the admin user settings
  4. enable the new UI in User Interface
  5. find the alerts stuff (System Settings -> Alerts)
  6. enable alerts
  7. then enable the alerts you want
  8. disable the new UI to have a functional interface

I think I'm going to look more into the TP-Link Omada stuff.