How to protect offline-android application from copying?

Question

Android

An application was developed on the ionic framework .
After it was published, it turned out that on most devices (even without root rights) it is installed in such a way that it is easy to simply copy it with an ordinary explorer and transfer it to another device and install it.
The features of the application are that it must first of all work where there is no Internet.
Therefore, all online checks, as a protective mechanism, are not suitable. To the point that even immediately after installing the application, a person can run it for the first time without access to the Internet. Application for Sailors, calculator. The Internet is very expensive on many ships.
I will listen to advice.
PS: given the features of ionicframework
PSS: In general, there is no answer yet. Only advice where to dig. I'm hoping someone comes up with an answer.

Answer 1

Use DRM
androidnik.ru/chto-takoe-sbros-drm-licenzii-na-androide