It doesn't have an SD card slot, on top of having little internal storage. This is a common problem with eInk readers, even though many do run Android - they either don't have an SD slot at all, or if they do, it's SDHC (and thus 32 Gb).

With K1, I have a 400 Gb card in there that's loaded with stuff - not only my entire Kindle library, but also Kiwix loaded with offline Wikipedia and a bunch of other wikis, OsmAnd topo maps etc. Between that, and several days of battery life with occasional use, it's perfect for multi-day hikes out in the boonies.