firmware-setup is a UEFI driver that implements the user interface for System76 Open Firmware. It is basic by design, with its only functionality being selecting the boot device and changing the boot order.
As a basic test, the driver can be loaded in QEMU to use the UI.
make qemu
In QEMU:
Shell> fs0:
FS0:\> load release\system76_firmware_setup.efi
FS0:\> exit