I know Graphene has a really helpful web installer that basically takes care of everything for you.

However, it assumes that you have a stock device with a locked bootloader.

Can I use that installer (or do I have to install it another way) with an unlocked bootloader running something other than stock OS?

Or is my device in such a state that I can't even use Graphene?

    "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."

    Source: https://grapheneos.org/install/cli#prerequisites

    Seems like it might work!

    phonehelp It's not a problem. The OS on the device has absolutely no involvement in the flashing process since it's done from the fastboot mode provided by the firmware. The devices prevent modifying the firmware due to verified boot.