I have exported an eBook project as an ad-hoc android app and have successfully launched a test release on the Amazon app store.
I can download the test app and open it on my Samsung Galaxy Tab A6 running Android 5.1.1, but it opens to a page displaying a Pubcoder logo and freezes there.
This is one of the eBook projects I am having a similar problem with opening the xpub version in pubreader (it opens to a blank screen).
I notice when downloading Pubreader from the Google Play store there is a message saying the app may not be optimised for my device.
Perhaps the issue is that my device is too old, and more recent devices would play the android app or xpub file without any problems. Which would be frustrating because I've just purchased this device specifically for the purposes of testing, based on advice that Pubreader works on Android 5.0 and above.
Still trying to find a solution to offer Android users for my books...