As spotted by TheGamer, the mod was created by MrHuu with details posted on GBATemp. You'll need to own a legal copy of the original game to migrate the relevant files over to the 3DS (which, of course, needs to be modded), but overall, it sounds like a relatively painless way to play the game on something that isn't the Steam Deck.
You can use the 3DS stylus in place of a mouse to interact with the game, though it's also noted that you'll need to press the 'L' button to cycle between left and right clicks. Sounds a tad fiddly, but we imagine it wouldn't take too long to get used to.
Otherwise, yeah, this is Fallout, on the 3DS. Neat! The only official Fallout release on the Switch, meanwhile, is Fallout Shelter which, don't get us wrong, is perfectly fun in its own right, but it would be splendid to get a port of Fallout 3. Actually, we spoke about that at length recently - go give it a read.
