[baobun]

Have you checked out uboot?

https://u-boot.org/

[franga2000]

Doesn't everything under the sun boot with uboot? Uboot is usually what people want to replace when they say "why can't this just run UEFI?"

[M95D]

I have yet to find a valid reason for UEFI to replace u-boot, or UEFI to exist at all.