DEC-850v1 Proxmox serial/USB installation

[N0b0dy1985]

Hi, this is outside the scope of OPNsense, but I've upgraded the memory and added a second disk to my DEC-850 with an eye towards moving to ZFS, and got to thinking that it would be awesome to install Proxmox VE as a host with OPNsense as a guest (I've done this on other machines, and it works pretty great, but those machines all had VGA/KB/mouse). There is a bunch of spare CPU/memory and disk capacity on this box now, and it would be great to put it to use. Proxmox shows support for serial-based installations.

Anyhow, I'm having trouble after I boot the Proxmox iso USB... on the console I see:

Code: [Select]

Welcome to GRUB!

error: no such device: /.disk/info.
error: no such device: /.disk/mini-info.


•     I've verified the iso hash
  
•     The BIOS is UEFI, latest version
  
•     The device is not configured for secure boot
  

My googling is failing me... I don't understand these error messages, or how to resolve them. Grub hangs and I can't proceed. Not sure if there's a BIOS setting that I need to touch. I've posted on Reddit and in the Proxmox forums but no luck yet.

Any help is greatly appreciated.