Yeah, it's based on Alpine, so it has the `apk` package manager, I'm not that familiar with it yet. There are three interface options: Gnome Mobile, Phosh, and Plasma Mobile. Phosh is developed by Purism SBC as part of the Librem 5 project.
Hard work!
https://wiki.postmarketos.org/wiki/Phosh
Where did Phosh originate from? which company?
Is alpine linux running under phosh?
Discussion
The issue is roots. The challenge I see with Graphene is google cost centralization roots. Cannot escape, only choice is start fresh of course built on open source.
Look for the cost centralization roots.
To build a new hardware path is requires lots of $$$ and plan.
Try track the roots of this Pine project.
I cannot do it without venturing into Chinese culture :)
Good work you are doing to dig into this!