I have a 256GB USB drive formatted FAT32. When I use a USB-C OTG cable to connect it to my Samsung Galaxy S8 (Android) phone, the phone can see the files on the USB drive. When I plug the same into my Oculus Quest 2 headset, I can't see that the USB drive is recognized. My OQ2 is working in other respects, including with a USB-C cable to a Win10 PC, and able to run Oculus Rift games such as Asteroid Shooter via Oculus Link.
Neither does. Facebook decided the option to connect to a PC through link was a higher priority than external storage/file access. Even though I would have loved it I agree with them.