[stumped]

i read a bit more also- the stick uses a protocol called WEBDAV and says that any device which supports that should have browser access, even devices that cannot run the sandisc mobile app.

what I don't know is whether the "experimental" kindle browser supports WEBDAV.
but Amazon kindle support should know - I'd ask kindle customer services or ask in their new kindle customer forum

PS the format used to store files on the stick should not much matter as the kindle will never be directly linked. I'd guess FAT32 as that is the most universally accepted, and the manual says that both PC and MAc are supported. ( though that would restrict use of stick for video streaming, and cast to TV is also a promoted feature )

a separate google search for WEBDAV is encouraging. and there are some ( albeit ancient) MR threads that mention webdav also