Confused about whether my iSCSI share is available/how to make it so

Question

I am attempting to set up iSCSI with a virtual machine as the initiator and the host as the target. I was looking at these instructions, among others: https://www.tecmint.com/setup-iscsi-target-and-initiator-on-debian-9/ and https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/virtualization_administration_guide/sect-virtualization-storage_pools-creating-iscsi-adding_target_virt-manager

I suspect that my LUN is not set up correctly, because tgt doesn't seem to know where the backing storage is:

$ sudo tgtadm --mode target --op show
Target 1: iqn.2018-11.ubuntu:ssdShare
    System information:
        Driver: iscsi
        State: ready
    I_T nexus information:
    LUN information:
        LUN: 0
            Type: controller
            SCSI ID: IET     00010000
            SCSI SN: beaf10
            Size: 0 MB, Block size: 1
            Online: Yes
            Removable media: No
            Prevent removal: No
            Readonly: No
            SWP: No
            Thin-provisioning: No
            Backing store type: null
            Backing store path: None
            Backing store flags: 
    Account information:
    ACL information:
        ALL

But as far as I can tell, the configuration file is set up correctly:

$ nano /etc/tgt/targets.conf

include /etc/tgt/conf.d/*.conf
<target iqn.2018-11.ubuntu:ssdShare>
 backing-store /dev/nvme2n1p1
 backing-store /dev/nvme1n11
</target>

and according to the webmin panel I set up, it looks OK as far as I know:

I am suspect that this is why I can't provision a virtual machine with the drive I am sharing via iscsi:

So my questions are:

1. Does the lack of a device path in the output of tgtadm explain my inability to provision the VM?

2. If so, what else do I need to configure to make that happen?

3. If not, where else should I look to figure out what's wrong?

Edit: Also, what is backing-store /dev/nvme1n11? It's not a device that exists on my machine or ever has, and I did not add it. In any case, deleting that line did not help, but I am confused as to how a non-existent device path ended up there.