@tuxlife oh btw
./mk -b coreboot qemu_x86_64_12mb
qemu-system-x86_64 -m 2G -smp 4 -bios bin/qemu_x86_64_12mb/seauboot_qemu_x86_64_12mb_libgfxinit_corebootfb.rom \
-drive id=disk,file=/home/leah/Downloads/debian-12.8.0-amd64-netinst.iso,if=none \
-device ahci,id=ahci \
-device ide-hd,drive=disk,bus=ahci.0
you can use u-boot in qemu, on libreboot.
you could probably just mess with it there if you want, to try changing video modes. then adapt for real hardware once you're ok.