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ChromeOS Flex, I suppose? Be careful, remove all drives. Leave only drive where you plan to install ChromeOS Flex. (Btw, I wonder if there is any way to create local user instead of google account).
So I'm not having any luck with any images I'm trying for Chrome OS. My guess is the fact that it's a Xeon processor that doesn't have an iGPU and only has a dGPU (Radeon 7970) in my case. Chrome OS Flex works, but of course no play store. But I do have Prime OS which is an android distro so the play store works on that. So what I am doing is using the brunch framework and creating a Chrome OS image file. Then burning that to an SSD, and then just plopping it in one of the extra drive bays. I've got 3 extra ones to play with so why not! I've got my main SSD's connected to the OWC Accelsior S PCIe's, 2 of them, and 1 SSD so far in bay 1.
 
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