The Imaam at our Musjid recited the Jumuah Khutbah from his smartphone.

Answer

Certainly it is improper and not permissible. Only an evil molvi will recite the khutbah from a smartpone which contains the filth of immorality, etc. Furthermore, even if the phone does not contain porno filth, then too it is not permissible to abandon the Kitaab for reciting from the phone. The many mistakes is an indictment against the molvi who has abandoned the standard practice of the Ummah – a practice of many many centuries to recite from a sacred Kitaab.