Though, as the narcs are quick to point out, Android 'is' Linux.
So really, the alternative is proper GNU/Linux (or as I've recently taken to calling it...)
Android uses Linux but it has no consequences for users or developers. So this is practically irrelevant.
See also:
https://news.ycombinator.com/item?id=50057296
It really isn't, it more like Inferno would have replaced its kernel with the Linux kernel.
It is as close to GNU/Linux as Inferno was to UNIX System V.
Which is why Termux has to work around what is actually available as public APIs on the NDK.