> think getting mainline Linux on viable and sustainable on multiple hardware devices is warmer, fuzzier foundation.
You just have to somehow speedrun the decades of development that went into Android to make it decently run on mobile hardware.. never really understood this "throwing out the baby" direction - the UNIX userspace model simply doesn't work on mobile (I would wager it also doesn't work on desktop anymore), has no security (everything runs as your user which made sense when you ran some batch job on a terminal with multiple other users, but nowadays when a single user has as many processes as all the user had back then it effectively means no security between any of those programs), there is no real resource control, no lifecycles, so the device will burn scorching hot and have terrible battery life.
On Android (and iOS) apps were always living in a world with lifecycles so if they wanted to operate correctly, they had to become decent citizens (save state when asked, so they can be stopped and resumed at any moment). This also fits nicely with sandboxes and user permissions, etc.
So without developing an alternative user-space for "GNU-Linux", it's simply not competing with android in any form or shape.
And even if you do, now every GNU app has to somehow be ported to that userspace API (you can't just kill GIMP or whatever Linux process)
The closest I got to Linux mobile is GPD Pocket 4 with LTE and regular apps. Since I can get it to cap at 5 watts, it can give 9 hours of battery life. It does most things I care about, but it is just a mini laptop (which is good enough for me).
> You just have to somehow speedrun the decades of development that went into Android to make it decently run on mobile hardware
Isn't this mainly due to proprietary drivers and firmware?
No, just take a look at how long and smooth does a pinephone run with "GNU Linux" vs stock android.
Android devs actually backported a bunch of work to the mainline kernel with regards to low-level energy management, but that's only one half of the story. The other is your phone stopping unused apps gracefully, and being able to go back to sleep regularly.
The vast majority which lives in android userspace. The customer compositor, input stack, wlan daemons, etc, are all tuned and optimized for power efficiency. Also, these days, there is a lot of hardware controlled directly by userspace - it's not just the GPU. And those hardware are generally important for offloading a lot of conpute and reducing wake ups. Things seem to only be trending further in this direction.