There are smartphones A, B, C, D. On smartphones ABC, the application was tested successfully, but on smartphone D, the application crashes. There is no possibility to test on smartphone D. How to find out where the program crashes? Or what are the tools for testing android applications?
Make a build without obfuscation, upload it to Google Play as an open/closed beta, send a link to the user, let him install and post a crash report for you. From it you will find out where it flies.