Grub rescue after upgrade to 5.0 - can't boot mdadm RAID10

I have / on a nvme SSD and /boot on a RAID10 mdadm array.

After upgrading to 5.0, I get a grub rescue shell (can’t boot).

I tried booting a live CD and reinstalling grub, but it made no change.

Is there anything fundamentally different in the ability for Debian 10 base to read /boot
on RAID10 volume vs previous version of UCS?

At the grub rescue > the ls command shows my four spinning disks and the two msdos
partitions in each. All are listed as unknown filesystem.

UPDATE: The issue may be related to grub not seeing my nmve ssd which contains my /
I’m not sure if this is caused by grub update or OS update. The machine never could boot directly to the NVME due to its age, but it was happily booting from the RAID10 containing /boot and / on the nvme prior to the upgrade to 5.0

Try to start your system with

so you can see if your system will boot from your nvme with the new system

Best Ben

Thanks @BenSommer.

I was able to boot UCS 5.0 with SuperGrub Boot disk.
I had to “load RAID & LVM” then SuperGrub Boot was able
to find my UCS installation and boot it.

I think my previous attempts to reinstall grub were ineffective because
I didn’t include “–target=i386-pc”

My first drive that is part of the RAID10 is /dev/sdb

This is what fixed my bootloader:

grub-install /dev/sdb --target=i386-pc