Planny is great, because it's completely designed to work great with Apple software. At the current time there are no plans to release a version for Android devices.
Instead there are plans to release a web version of Planny that works with iCloud. Many people at work have to use Windows or Linux and love to use Planny at home or on their smartphones. Therefor a web client is developed starting next year. This version will ship in Late 2019.