Power on the Nimbustor via the power button - keep hitting esc on the USB keboard 'til you get to the BIOS menu
Select 'boot manager' and choose the installer pendrive from the list to boot off it
Debian will boot - choose the option 'install' as we need to use the non-graphical install since we have no mouse ( not enough USB ports )
follow the prompts
You'll get a warning about the rtl8125 firmware - select 'no' (the NIC will work fine without it for now)
Carry on, selecting a hostname and domain name as required
Set the root password
You will be prompted to create a non-root user - fill this out but be aware this user will be deleted later ( OMV6 needs to create/manage users - so we need to delete it and then re-create any required non-root user accounts inside OMV6 once it's installed)
You will be prompted for disk setup - choose 'guided - use entire disk'
Select your USB system drive - make SURE you do not accidentaly select the eMMC ( it's too small, it has the ADM bootstrap on it so is needed if you ever want to be able to revert to running ADM - and it doesn't have the write duarability required anyway)
Select the option 'all files in one partition' ( we'll be creating the raid arrays on the HDDs later inside OMV6 )
Since we plan to install OMV6 to allow web management we do NOT install a graphical system - it's not supported with OMV6, plus if you've only got the stock 2gb RAM it's too memory hungry - so unselect 'debian desktop environment' and 'GNOME" and select 'ssh server' ( so we can login via ssh to manage the system )
proceed thru the setup, at the end it'll reboot and boot off your new install
login on the console as root
enable ssh root access
nano /etc/ssh/sshd_config
find the line '#Authentication' and directly under it add a line
PermitRootLogin yes
save and exit, and restart sshd ( service sshd restart )
Delete the un-needed non-admin user account created during install
userdel <username>
rm -rf /home/<username>
Login from your computer using your preferred ssh client and proceed to next step