They did it. A mad man finally did it. Someone found a way to mod a backplate and Deck to fit a 4TB 2280 NVMe drive onto the backplate of a Steam Deck, rather than use the much smaller internal 2230 drive. The someone in question is Reddit user mikerfx who made a Reddit post about what he has been working on:

4TB NVMe Mod

What you see in the image above is a backplate to the Steam Deck that has had a hole cut out on the bottom that is the same size as a full sized NVMe drive (instead of the smaller one that is in our Decks from Valve). He then placed a caddy around the hole, which holds the NVMe in place, and uses a ribbon to attach it to the internals of the Deck:

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This is actually an incredibly smart move of him to do. Lawrence Yang on Twitter made a note that trying to modify the internals of the Deck with a bigger drive will evidently harm your Deck as it draws more power and gets hotter than what the Deck is designed for. Mikerfx semi-skirts around this by having the NVMe drive lay in the caddy on the backplate, so it isn't internally in the Deck. This will theoretically avert any issues with increased heat coming from a significantly larger drive. In terms of power draw though, mikerfx has said in a comment that the power draw so far has been fine. And in the end, with all the reconfiguring, it is recognized in the system:

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This needs a lot more testing, but it does show the ingenuity of some people to find ways to make things like bigger drives and more storage space work. I am looking forward to seeing more of these kinds of modifications and how they will find ways to make it work, while mitigating power draw and heat. You can also go over to his post and see some other screenshots he has taken of the modifications. And of course, upvote him to karma heaven!