Questions about blade server SSDs [ANSWERED]

I recently bought a used blade server on the cheap (thank you LabGopher) to upgrade my home set-up and got one in pretty good shape. This is my first foray into blade servers and as I'm in the process of setting it up I'm running into some questions where I'm in a bit over my head trying to figure out.

The server has 4 x 3 TB SAS SSDs. I've installed Ubuntu Server 22.04 just fine. However these four disks show up as a single disk with all the partitions on it. fdisk and similar tools all just show a single sda drive. Furthermore, the total size of that combined disk is shown as 8.4 TB instead of the expected 12 TB.

Clearly I'm running into the 2.1 TB disk formatting limit on each of the four drives independently, but I'm not sure how to proceed. Ubuntu can't even see the missing space. My questions are:

1. How do I recover my missing 3.6 TB? If I expand the partition to include all free space I just get the 8.4 TB, so it seems like it's a deeper limitation than just the OS, which I don't know how to handle.
2. How do I get the drives to be individually visible? If I want to set up software RAID I need to have multiple devices accessible, instead of just this conglomerate drive.