Flashing grub_kcma-d8-udimm_2mb_libgfxinit_txtmode_usqwerty.rom from libreboot 20210522 on a KCMA-D8 with eight ACTICA act4ghu72d8h1333h DIMMs and 2MB chip results in no output on screen after reboot.
For now, my workaround has been to flash back externally libreboot 20160907.
Can you try the rdimm roms instead?
Also, please send logs. e.g. coreboot log, using serial port
raminit is usually the cause of boot issues on these platforms.
i have a d8 here that i'm testing soon. i'll test it myself