Hey, so I don't post anywhere else except discord really, so I was hoping someone else who is more prolific on other sites could spread this info around, as I was unable to find this suggestion anywhere when trying to troubleshoot this drive detection problem.
I recently upgraded an Xbox One S's internal storage, and sold him his old hard drive back in an enclosure so it could be used via usb 3.0
The trouble was, the drive would not show up on the Xbox as either media storage or as game storage. Even formatting the drive did not resolve the issue. I decided to take a crack at something as a shot in the dark and it worked.
I initialize all drives with GUID Partition Tables, and indeed this disk was already GPT when I removed it from the Xbox. Most off the shelf drives use the older Master Boot Record standard though. I converted this drive from to an MBR disk, and ouala, the Xbox now recognizes it as game storage.
To convert a disk to MBR, if anyone has this problem themselves, open up the Disk Management utility in Windows, or on Linux you can download GParted. On Windows, delete all partitions on the drive, right click on the drive at the lefthand side of the window, and select "Convert to MBR disk". On Linux the process just entails selecting the drive and going to the toolbar and selecting "Create Master Boot Record"
When you're done, create a new partition in the NTFS format, as the Xbox will not recognize the drive without a partition.