For BIOS/UEFI a lot of hardware vendors outsource their firmware to AMI and AMI keeps everything proprietary so they can keep charging money.
(Coreboot is not an option for real computers because it doesn't have menus and various other things.)
(Coreboot is not an option for real computers because it doesn't have menus and various other things.)
System76 have built a more serious setup UI: https://github.com/system76/firmware-setup
Microsoft’s https://github.com/microsoft/mu also probably contains UI from the Surface line or something??