Official comment
Sorry, there are just too many out there for us to test them all and provide a full list - the best thing to do would be to have users report which ones they use, what format, and which gear they use it with.
We know some USB3.1 drives won't work in certain players, and some USB2 or 3 drives won't work in others. Sometimes if the drive is formatted FAT32 it's not as fast as HFS+... there's just so many small things that make a difference!