This small utility when run will set the OsIndications UEFI variable for booting into firmware setup.
RTFM (it has a manpage!):
https://gitlab.com/JohnoKing/os-indications/-/blob/master/os-indications.8
https://gitlab.com/JohnoKing/os-indications
see-also:
https://blog.fpmurphy.com/2016/04/uefi-os-indication-variables.html
Intel blogged on OsIndications, but they changed their site and the post is apparently is no longer available:
https://software.intel.com/en-us/firmware/library/using-os-indications-uefi
Firmware Security 