Which isn't part of the public APIs,

https://developer.android.com/ndk/guides/stable_apis

I'm not really sure what your point is

the NT native kernel API is also undocumented

Exactly, that is why applications that don't want to break with each OS update don't touch those APIs, making them irrelevant for application developers.

Also, contrary to Windows, since Android 7, applications that link to undocumented APIs get terminated as security measure.

Ask the termux guys how much fun they are having by refusing to acknowledge the fact that they have to use JNI and not Linux syscalls for their stuff.

> Also, contrary to Windows, since Android 7, applications that link to undocumented APIs get terminated as security measure.

"undocumented" has nothing to do with it

there is a sandbox, syscalls are checked by seccomp and those not explicitly permitted will result in termination of the application

it doesn't care where the syscall comes from, be that libc, golang style, or calling svc #0 yourself

additionally: the kernel is open source... there are no "undocumented" syscalls

this also has nothing to do with the original point

Sure it has, because it doesn't matter if it is open source or not, if it is a stable API described on the NDK documentation it is not allowed.

Something that termux guys are having some issues to swallow, regarless of Linux being the kernel, it is not allowed to do what they want, wrapping Java APIs via JNI is the only allowed way.