ilarion has the right idea. you will need to set the disk controller to IDE.
along side this I had the following set in my template (Unraid GUI)
Machine: i440fx-5.1
Bios: SeaBIOS
Primary vDisk: manual and set to the qcow2 you extracted
Primary vDisk Bus: IDE
Graphics Card: VNC
Network Model: vertio-net
I have set up a few CE installs on Unraid without too much issue. Feel free to ask additional Q's