For the followers and owners of the Asus Zenfone Max Plus M1 I have sad but expected news: there is no new firmware updates available in June 2019. That means that the update version WW-15.02.1904.453 is the latest available update. It brings Google security patch 2019/5, but apart that nothing new.
All the issues following ZenFone Max Plus since firmware update to Android 8 Oreo are still not fixed. There has been some news that the phone will receive an update to Android 9 Pie, but they have all died out.
Judging by the feedback on the official forum, phone owners seem to give up on this phone and claiming never to buy another phone from Asus. Official forum replies still seem to be only pre-written general copy/paste replies without any value to the person asking, so their wrath is understandable.
My assumption is that this particular device is already forgotten by Asus – even if it’s still available for sale in some countries. They are moving their developers to newer devices like this years flagship ZenFone 6. However tempting it might be for you to own it, just keep in mind about the disappointed owners of ZenFone Max Plus. If you buy the new model, next year you might be one of the forgotten users with a broken phone and software issues beyond repair.