Mautic records devices used to visit pages and open emails.
To detect devices Mautic uses Piwik Device Detector. Please be sure you have this library installed in your Mautic instance.
Every page and email created with mautic should detect the device used to view a page or open an email.
Emails need to be sent from a public instance of mautic in order to test open actions, or you can copy the tracking pixel URL and paste it in an incognito window of your browser to test in a local server.
Any page or email that has Mautic's tracking pixel should detect the device used to view a page or open an email.