Thanks, but the "badboot" log doesn't seem to show the failure.
Apologies, not thinking again. How about that one?
Also, I note the enclosure gets lower boot priority than the onboard SSD when on the USB 3.0 port, but not when on the USB 2.0 port. Do I need to do something to the bootorder file for USB 3.0?
Your boot order file only seems to extend to ports 1-7, while it looks like the controller defines up to 15 ports. (In particular, it looks like port '/pci@i0cf8/usb@14/usb-*@c' is needed.)
Thanks for the tip, I'll try fixing that up.
John.