Kobo's newest ereader ships without an external card slot, limiting the average user to only 8GB of storage. That's just not enough for everyone, which why some Kobo owners have taken to cracking open their device and replacing the internal microSD card found on some models.
Alas, that won't be possible on the Aura H2O (2017).
I cracked open my unit today and found that there is no internal card slot:
This was to be expected; the Kobo Aura H2O (2017) uses a waterproofing process that involves coating the internal electronics with a water-resistant goo.
The Aura One uses a similar process, and so does the after-market Kindle from Waterfi. That process doesn't work with card slot, which is why the new Kobo Aura H2O (and the Aura One) don't have card slots of any kind.
It's a shame, but also one we were expecting.