well dsm/xpenology is a appliance and in some points restricted, imho best alternative when it comes to plugins/docker (ZFS based is not a real comparsion here, dsm does not have this) is open media vault (omv), looks nice and it still my fallback if dsm is not going to work for me, it can use the lvm/mdadm raids created from synology so you can boot up ant instantly use your data raid (i tested this with a raid6 from dsm, not tested with SHR raids)   you can still buy a used 8port con