Ver 1 of XOSTOR being released today, as part of XOA 5.94
Take off with XOSTOR (xen-orchestra.com)
I believe you need a license for XOSTOR, and is not included in the free version of XOA (I may be wrong)
You’ll probably have to build it from source then.
I think XOStor is still going to be closed source and for pay.
But, there might be a command line way to get this working. I’m very interested in this even if it is just a backup to my main storage. It’s nice to have a place to move your VMs when you need to do work on your NAS.