Hey Jim,
Even if it is repeated again and again, this is not true. USB 3.0 flash drives work perfectly on the Onefinity Controller, because every USB 3.0 device is downwards compatible by design.
What might not be supported because of the age of the underlying Operating System in the Onefinity Controller, is exFAT Filesystem found on practically every USB drive bigger than 32 GB nowadays. If your flash drive is not recognized by Onefinity Controller, you have to reformat the flash drive using NTFS or FAT32 instead.