foxjaw This doesn't make sense. It's highly insecure and not fully functional. GrapheneOS is not only a system image. It's an OS which makes changes to the kernel, etc. It cannot function without the kernel changes. Supporting a device without updating the firmware, drivers and kernel is highly insecure and does not make sense for a hardened OS.
The only use for a GSI release is development/testing. The only use for GrapheneOS would be reusing a single system build across devices instead of building it for each, but that doesn't change that the OS is much more than the system image.
foxjaw Fairphone doesn't meet our basic security requirements. Releasing a GSI by itself is incompatible with shipping a secure OS.
https://grapheneos.org/faq#future-devices
I know it comes with all FOSS out of the box
This is not correct and not the intended purpose of the device.