If you're after Salt V in Dulux, your two best bets are Dulux Misty Mountain and Dulux Rockpool Ripple, both landing at ΔE 2.2 from the original with an LRV of 45.3. A ΔE under 2.5 is what we'd call very close — most people wouldn't clock the difference once it's on the wall, but a side-by-side swatch in raking light might just reveal it. It's not an imperceptible match (that'd be under 1), so go in with eyes open.
Both Dulux options sit at the same measured LRV, so they'll bounce light the same way and read as a mid-toned, restful colour — neither dark nor pale. The choice between the two comes down to the subtle undertone you prefer in your own light, which is why you should never trust a screen for this. Order both as peel-and-stick samples or brush a generous patch and live with them for a couple of days.
Now, the honest bit: Paint & Paper Library colours are formulated with a layered depth that's part of why people pay for them. Salt V has a particular quality that a colorimetric match gets you most of the way to, not all of it — especially in their richer finishes. If the exact character of Salt V matters to you in a feature room, I'd spend the extra and buy the real thing. If you're painting a hallway, a rental, or a big surface where budget genuinely counts, the Dulux match at ΔE 2.2 is a sensible, sound call.
Whatever you land on, test it against the surface it's actually going on, at the time of day you'll see it most. North light will cool both these colours; warm afternoon sun will lift them. Match the finish too — sheen changes how a colour reads as much as the pigment does.