ADD POOL using unformatted disks (blkdiscarded SSD's) fails with the following error messages:
A 2 device pool
emhttpd: /mnt/test mount error: No pool uuid
A 1 device pool
emhttpd: /mnt/test mount error: Unsupported partition layout
The workaround is to preformat the drives using Unassigned Devices
Tested in Safe Mode, with the disks connected to on-board Intel controllers.