Add drives to a Linux RAID for more storage

My 6 Terabyte 4 drive RAID 5 array was starting to get tight on space. Upgrading the motherboard to a GIGABYTE X570 AORUS ELITE gave me 6 SATA ports so I could finally populate the the two empty bays in my 6 bay ICY Dock enclosure. I’m adding two Seagate BarraCuda 2TB 2.5 inch Internal...