Update - I have been able to make progress.
(1) I have been able to get XO version 5.80.0 appliance installed. For some reason the automated web deployment method didn't work. Couldn't work out why.
(2) Had to reinstall xcp-ng again on the new host.
(3) Using XO appliance - had to add a number of interfaces prior to attempting to add to the pool.
(3) Using XO appliance - have been able to add the new host to the pool.
(4) Took a few reboots and manual powercycles to get the new host integrated into the pool and recognized within XO appliance. Shutdown/reboot would hang and not complete.
(5) The SRs had to be connected / disconnected / connected from the XO Host-Storage tab for them to be online and accessible. Couldn't use connect to all hosts from the Pool-Storage tab.
(6) Then finally success in moving VMs from the old host to the new host.
Phew... half-way there.