Note that this could include packaging Linux GUI applications as Android APKs (with some additional glue code and Wayland/DBus integration of course), so it's not even an either or.
> Why not try to fork AOSP or GOS
Which concerns do you share? Both AOSP and GOS must follow the Google development strategy, they aren't exactly independent on Google (which is a problem: >>45208925 ). Nevertheless GOS on Librem 5 or Pinephone would be a nice idea, except the GOS developers are against that: >>45101400
> Linux's (nonexistent) security model
Linux's security model is based on trusting the software you're installing from the FLOSS repositories, and it works very well.
GrapheneOS are against using their development resources on a platform that is drastically, significantly worse than the hardware platform they already have, which is quite fair. It is not about Pine64 or Purism's products specifically. They would not be against them if they met 95% of the requirements detailed in https://grapheneos.org/faq#future-devices. It would more sense to explain which of those requirements you think are unreasonable.