Hi Steve, I'm encountering the same problem here as Leah. In my case, my attempt was manual installation of Debian Buster (10.2) amd64 on my Supermicro X9DRL-3F running UEFI mode. My situation also followed the exact circumstances of OP in this StackExchange thread <https://unix.stackexchange.com/questions/541489/grub-fails-to-install-during-debian-10-installer-re-uefi-supermicro-motherboa> (including same X9 motherboard family).
Do let me know how I can help to provide more information to identify the cause of this issue. Best Regards, ZY
