how to install a XG home image on a modern hardware ?

Two thoughts/suggestions

For hardware that has compatibility and you can boot the installer (but the OS doesn't boot); I wonder if the issue is with the hard disk controller. Servers tend to use more sophisticated chipsets and there may be no support in the Sophos OS. You could try getting some basic PCI hard disk controller and connecting your hard drive to that.

For hardware with no compatibility option; Have you tried running the Sophos OS under a hypervisor? There will be some performance hit (I've no idea how much) but that may be a way out and give you more choice about your underlying hardware.

For such scenarios, customers get a HA (two appliances). You do not have to get an extra license to run this. Simply purchase two appliances and run the HA. 

The portion of customers running software "bare metal" is small. Virtual is another part of the story. 

No array just a one standard SATA drive plugged into the motherboard.  Everything brand new.  I have tried other drives and controllers but I know everything works as I ran another OS on just to be sure.

Yes, I have thought of the controllers but using several different types of servers and workstations there is no clear reason why some machines work and some don't.  I am currently running on an old Acer workstation.  It works but I don't have another one and I don't want to run on old hardware plus I need about 6 firewalls when I am done. 

Regarding hypervisor I thought of that but I like my firewalls to be on the bare metal.  It is the gateway to the network and I don't want Windows or even VMware getting in the way or worry about a vulnerability that will take down our network.  It's also another OS to maintain and patch.

You are right bare metal installs must be extremely rare as there is zero documentation on it.  I am all for HA and two appliances but we are under software contract for another two years so I can switch to an appliance. 

What about doing a Hypervisor setup in between? This would eliminate all limitations. 

Have you spoken to whoever supplied the licences and see if they can arrange a trade in for XGS hardware and new licensing. I don't know if Sophos do that sort of thing but some companies can be quite flexible, especially if you are experiencing the sort of issues you are.

I have not gone down that road yet as I thought this would not be as hard as it is to get this working.  Most likely there would not be much of a discount and it would cost us a lot more money then just buying the correct hardware that will work with this software.  This should not be this difficult.  

Thank you for the information but XG does not support UNAME or WHOAMI commands at the console.  It looks like most commands are disabled and I can't find a way to get the kernel info from XG.

That is really odd. I know for a fact it at least works on the UTM.

Uname also works on the XG.

ian