Hardware RAID is dead.

• They’re no faster than Software RAID today

• They’re vendor and often model locked to a particular make or model of card (so if your card goes bust, so does your array, where software options you can migrate the entire machine to a completely new one, as long as the disks are good so is your data)

• ZFS wants access to individual disks anyway

Check which raid card your Dell shipped with, if it’s a PERC H200 or H310, you can flash it to IT mode to make it work as a plain HBA. If it’s a PERC 700, you’re SOL on IT mode. I’m pretty sure it can expose vdrives, but that’s probably more trouble than getting a cheap HBA at that point.