App publishers all too often target the newest platform version without rhyme or reason.
There is a decision making process that favours doing this: They can upgrade their build environment and target most users, to which the response is to immediately proceed!
(The unheard counter-argument is that they could instead do nothing and target all users, but how many build architects would suggest that?)
If you have permission, you can convert APK/DEX to Java source code using a
decompiler and then try compiling the Java for a different platform. The danger is that dependencies might have different interfaces and be potentially time consuming to fix, so this approach could become a really big project.