The recommended method to convert these disks is to upgrade the operating system to Windows 10 first, then perform the MBR to GPT conversion. So 2k8 sounds like a no no even for an offline conversion.

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Turns out by default Linux (RHEL8) is still using MBR disks and so you run into the 2TB max limit. Found that there is a command "sgdisk" that will do a live conversion to GPT without any data loss.