In order to leverage IKEv2 within your Apple Configurator environment two areas need to be modified.
First the root certificate from the Untangle needs to be added under the Certificates option in the Apple Configurator. The Untangle root certificate can be found under Config --> Administration --> Certificates tab.
Second the VPN needs to be configured under the VPN option in the Apple Configurator. The following fields need to be filled out.
Connection Name - This is a reference name for administrators to quickly identify this VPN
Connection Type - IKEv2
Always-on VPN (supervised only) - ticked
Server - The hostname or IP address of the Untangle
Remote Identifier - Normally the same as the Server field, hostname or IP of the Untangle
Local Identifier - Can be left blank and the Apple devices IP address will be used
Machine Authentication - Certificate
Enable EAP - ticked
EAP Authentication - Username/Password
Account - Username configured under Local Directory on the Untangle
Password - Password for the above user
Here is a screen shot of the VPN page in Apple Configurator