[server] LXD passthrough AMD GPU on Ubuntu Server

I have seen only posts all over the web about using an Nvidia card (even Intel) with an LXD VM, but nothing about using an AMD card on a headless host.
I'm using the LXD Web UI:

• Allow GPU devices in LXD (Under Configuration > Device usage)
• I create a simple VM with desktop, no special settings.
• Starts fine
• I add this to the instance config under devices:

The VM just fails to start after adding the GPU config. Any help/suggestions is welcome.