Hi [NAME] W_2,   After changing to UEFI mode, On the System Setup Main Menu screen, click System BIOS. On the System BIOS screen, click Network Settings. On the Network Settings screen, click UEFI iSCSI Settings, are you able to see iSCSI Device disable and enable?
I have a Dell PE R730 I was hoping to diskless boot ESXi via iSCSI like I have setup with two R820s. However, even though all the spec sheets say the BRCM GbE 4P 5720-t rNDC supports iSCSI, the options to set it up in the LifeCycle Controller are noticeably absent; it says only PXE is configurable. Has anyone encountered this issue before? 
Dell R730 BRCM GbE 4P 5720-t rNDC - iSCSI boot protocol missing