Android runs toybox (or at least used to), which implements many of the GNU tools. But I think the complaint is that much of the userland to have a useful phone experience is proprietary.
If you could install all the GNU tools into AOSP Linux (probably not that hard), you still don't have a useful phone.
It's not even the desktop environment (think GNOME/KDE/etc.), as there is a good enough version in AOSP.
All it takes is one good phone application that uses the underlying devices.
Also as a reminder, WebOS is also Linux and the Palm Pre phones were excellent phones (with a somewhat limited app support - they were a bit ahead of time with JavaScript and applications written on it)
Why is the title “Is there hope for linux on smartphones?”?
If it said “Is there hope for GNU on smartphones?” the answer would be a resounding no, because the community is fractured and politicized to the degree the products are uncompetitive. Pinephone is an example. Then there was the Ubuntu effort.
Android, being partly closed as the GPL2 allows for, is proof that Linux can be highly successful without the GNU crowd. And perhaps they should stop taking credit for software they didn’t write. They made the license.
For all the complaining, the free software community hasn’t designed from the ground up and released one single production class handset alternative at a time when the culture consumes in the billions. That’s says a lot. The infighting and utopian idealistic virtue signaling is in sharp contrast to the reality of the platforms the GNU crowd has built.
Just the kernel is Linux, but with the "Linux" that is meant here, it has basically nothing in common, be it e.g. in the userland or "the spirit".
The Linux from "Linux Smartphones" e.g. fosters an open, user-first ecosystem, as opposed to the often very closed and locked Android Smartphones. Another examples are e.g. Safetynet or the Google Play Integrity API. Those primarily don't server the users. Or apps that either complain or even stop working on rooted phones. We have admin/root on normal PCs and nobody is complaining there.
Linux is only a kernel. What most people mean when they say “Linux” is actually “Linux distribution” which is the Linux kernel plus some userland like GNU or Android.
Just the kernel is linux, but isn't basically all of the hardware support we need in the kernel?
Sure, we're still out of luck with trying to run mainline kernels, but what's stopping us from running normal GNU userland on top of a working Android kernel?
Not having your images and messages scraped or getting tons of spam is in the interest of users. Those API allow developers to offer a better experience to users by being able to know if people are running a trusted version of the software.