> People forget that Linux is the dominant kernel/os because it dominates nearly every market that isn't the desktop (server/mobile/IoT/toasters).

This is mostly correct while referring to the kernel. Nevertheless, a kernel by itself is just one component of the low level system. And I personally definitely do not consider the Android experience a "GNU/Linux" one - even the base libc is replaced with a quite broken (e.g wrt POSIX) Bionic. This is leaving aside all the firmware issues, lack of administrator control without "rooting", etc.

So in other words: it is natural to "forget" that Linux is widespread on mobile devices, simply because the experience is extremely different.