Asus had uploaded the new Android Pie 9 software for Zenfone 5 a few days ago, and many of you have already downloaded the same manually. But, in case you haven’t, Asus will soon send an OTA notification for the update.
The new firmware update carries the version number V16.0610.1812.58. It includes the Pie OS as well as a a new security patch (not entirely clear which month, however). Besides that, there are no major changes to ZenUI and the pre-installed apps.
Note that the update is pushed out in batches, so you may not get the notification right away. You can go into the Settings > System menu to check for the update manually.
The higher-end Zenfone 5z is already moving over to Pie – an OTA update was delivered to Taiwanese units just before the end of 2018. A wider distribution should start soon.