TrueNAS SCALE expects you to deploy Kubernetes clusters, it is unfortunately not meant for running plain Docker. You can jump through hoops to get it working but I personally gave up and ended up running a VM on top of TrueNAS just to run Docker on it.
I don’t know about Unraid though and OpenMediaVault felt a bit unpolished the last time I used it and I can’t attest for its ZFS support.