Ubuntu 18.04 server failed grub install

[scjones5]

I am trying a fresh install of Ubuntu 18.04 server, without an internet connection (not Live) on my Dell PowerEdge R640. The machine came with a Boot Optimized Storage SSD (RAID 1), which is where I'm trying to install to. However, when the installer attempts to install the grub boot loader, I get "Unable to install grub in dummy 'grub-install dummy' failed". Has anyone encountered this and/or know what my issue is?

Thanks in advance!