Rogue's Elusive states " No attack roll has advantage against you while you aren’t incapacitated." and Stalker's Flurry states "Once on each of your turns when you miss with a weapon attack, you can make another weapon attack as part of the same action."
Does Elusive work against Stalker's Flurry? By RAW is Stalker's Flurry the same as attacking with advantage or somehow different?
Stalker's Flurry isn't advantage, because it's an actual separate attack. The two features don't interact; Elusive provides no benefit against it (aside from possibly canceling actual advantage, if applicable).
As a note, even ignoring stuff like Elusive, Stalker's Flurry, despite the surface similarity to advantage, is different. It can stack with advantage, unlike actual advantage; if you have advantage on your first attack and miss anyway, you still get to attack again (for a total of three d20 rolls for something to hit, four if the condition granting you advantage persists for the second attack). It isn't canceled by disadvantage either, and is in fact more likely to trigger if you're suffering from disadvantage. And if an effect applies to only one attack roll, for whatever reason, the second attack granted on a miss will not benefit from it.
In short, don't think of Stalker's Flurry as advantage. Aside from a vague similarity on the resulting probabilities when you have neither advantage nor disadvantage, it's not the same thing at all.
Elusive states:
Beginning at 18th level, you are so evasive that attackers rarely gain the upper hand against you. No attack roll has advantage against you while you aren’t incapacitated.
Nothing here says anything about preventing additional attacks being made against you, so it doesn’t do that. There is simply no interaction between Elusive and Stalker’s Flurry, except that the attacks made against the rogue cannot be made with advantage.
