When Amazon thankfully corrected their device specification page and changed the USB port from being for “Accessories Only” to being for “Accessories and media storage”, it seemed to indicate that a USB drive connected to the 2nd-gen Fire TV would not accept app transfers as is the case with the 1st-gen Fire TV. I have confirm that that is in fact the case. Apps on the new Fire TV can only be moved to a microSD card, not a USB drive. A connected USB drive does not appear anywhere in the new Fire TVs settings menu. It does, however, get mounted and its contents are fully accessible at /storage/usbotg by any app, such as Kodi, so the media storage capability is accurate. Limiting app storage to the microSD card was likely done to simplify the interface since you can have both a microSD card and a USB drive connected and mounted simultaneously. Amazon likely didn’t want customers juggling apps between various external storage devices. The microSD card can also be accessed by any app at the directory /storage/sdcard1.

Amazon has partnered up with SanDisk to release official microSD cards for the new Fire TV. These cards come in 16GB, 32GB, 64GB (currently unavailable), and 128GB sizes and are class 10 performance with speeds up to 48 MB/s. These microSD cards state that they are “the only ones tested and certified to work with your Fire Tablet and Fire TV.” Of course, that doesn’t mean these are the only brand microSD cards that will work. Just that these are the official ones and will likely be the brand of 32GB card that is included with the new Fire TV Gaming Bundle. The cards can be pre-ordered now and will be released September 30th.