Since there is no "official" Alpha 3 app for mobile, GameJolt has become the primary hub for fan-developed versions. When searching for you will typically find:
You may find base projects, such as those by Harveyyoyo , which provide a template for mobile Hello Neighbor games, sometimes including Alpha 3 assets. Installation Guide for Mobile (GameJolt) hello neighbor alpha 3 mobile gamejolt
This version debuted a more reactive AI that learned from player behavior, placing traps like cameras and bear traps in frequently used paths. How to Find Alpha 3 Mobile on GameJolt Since there is no "official" Alpha 3 app