Old Dell PERC H310 with kmod-megaraid_sas and Rocky 9.4 Cant see controller or disks

Hi,
Turns out that if I boot the Dell Precision 5600T in legacy mode then the stock Rocky 9 kernel / installation process can see the disks on the H310 and this is without any additional kmod from el repo. I had installed it using UEFI mode, on the first internal SATA hard disk.

Now I don’t completely understand why but suspect because there is no RAID configuration and the 2 data disks are “handled by bios” according to the H310 firmware splash notice - which I thought meant the BIOS on the H310 rather than the server’s BIOS - the server BIOS see’s these 2 disks only in legacy mode because they had been previously used aka formatted and partitioned as non UEFI data disk then.

To be honest I’m guessing and think I need to read more about the actual differences between legacy and UEFI and it’s strengths and weaknesses. Especially as I am often handling hardware that’s more than 10 years old.

Thank you for your time.