The Limine registration helper rebuilds the UEFI BootOrder from the
pre-state read, but passes every entry through verbatim. Some firmware
(listed in the BootOrder but with no matching BootXXXX variable) causes
efibootmgr --bootorder to fail with exit status 8, aborting the whole
install at the bootloader step.
Only carry forward entries that still exist as boot variables.