TerrapinX What Android version should be installed on a Pixel 5 before attempting an install of GrapheneOS ?
From the Web installer page:
"It's best practice to update the device before installing GrapheneOS to have the latest firmware for connecting the device to the computer and performing the early flashing process. Either way, GrapheneOS flashes the latest firmware early in the installation process."
I would just update to latest official version and start from there. Web installer should flash Android 14 based legacy extended support release.