Does that only involve unchecking the option in Unraid on the flash drive? Or is there more to it? I tried just booting the 2nd USB partition that isn’t listed as UEFI but got an error. Reason for this, I cannot boot into GUI mode(it goes to a flashing cursor), and using Legacy boot was a proposed solution.

To boot legacy/CSM you don't need to do anything to the flash drive, just select the appropriate boot option in the board BIOS, if legacy/CSM boot is still supported/enable.

I'll double check my bios. But I'm pretty sure legacy/csm option was enabled. When I booted the non-UEFI partition, I got some error like "this is not a bootable drive."

It's the same partition, if CSM/Legacy boot is enable you should get two boot options:

 

UEFI: Name_of_your_flash_drive

Name_of_your_flash_drive*

 

*Sometimes USB: Name_of_your_flash_drive

 

 

 

 

E.g. for typical Asus BIOS

 

Correct, I get both options. If I boot from the non-UEFI, it says it's not bootable. If I boot from UEFI, I can't boot into GUI mode.

Like mentioned there's nothing to change to enable legacy boot in the flash drive, see if it boots in a different system if available, could be a BIOS issue.

I can confirm CSM is enabled, and still getting not bootable error from the non-UEFI side. I only have 1 other OLDER machine to try, but I had similar issues with different drives when I first practiced Unraid with it. I can maybe try a different port, but strange that would matter.

It looks like I misread some of the solutions to this issue, and booting legacy wasn't it, just enabling CSM. But there are others, something about a driver integration and also a nomodeset option. I'm not at home, and probably won't be able to get to it for a couple of days.

I did get the GUI mode working by using GPU Driver integration. The AMD driver worked, but the Radeon did not.

 

Still having issues binding the GPU to an existing Windows VM. I'll detail in a separate post when I can.