You can already download the apk from release page and install it on any Android device:
It’s intentionally not available on Google Play store, as people who installed it on smartphones would complain the screen is too small for krita interface.
Maybe it will be enabled if there will be dedicated interface for mobile devices.
I use a recent build still in development, that you can get from this link, it’s a early 5.1 build that already have gestures implemented, it will officially be launched around June.
I will do an Smartphone guide for it when it officially launches, but feel free to ask any questions!
You can check this topic onwards for more information about this build and nice ways to use the UI.
Feel free to create a topic about it if needed.