Hello,
Correct, all EQL SANs are iSCSI only. Drives must be made specifically for them. It is not the firmware that determines compatibility. You will have to find EQL refurbished drives. OEM, Dell enterprise, or other Dell SAN drives will not work either.
There is no JBOD option with EQL. A RAID must be configured first.
So it's not ideal for ZFS. You could however, mirror the two SANs using ZFS. That would increase your HA dramatically.
To date I have only used TrueNAS core and recently SCALE with EQL SANs. I use ZFS to mirror volumes on two different EQL groups. The TrueNFS servers are running as VMs so the hypervisor handles the MPIO requirements quite well and provides HA. One benefit is that I could also use EQL replication to have two targets in different locations. Lot's of flexibility. ZFS intent is to deal directly with disks of course.
Just thought I would clarify some info about EQL even though this is an older thread. Hopefully, someone finds it useful down the road.
Regards,
Don