Neither Breitbart nor Assange had the philosophical weight (or ballast, or ambition) that Dugin was trying to push. Those guys were tactical, not strategic, or academic.
In the west, on the right, you are talking in the ballpark of the late Roger Scruton. Or, less eminent, maybe Curtis Yarvin (mencius moldbug). Or perhaps Houellebecq in France, but he has a rather different focus. The late Angelo Codevilla would have been there in a “big picture” sense, but, also, his focus was the US.
On the left - mainstream there arent really any big ideas guys that anyone knows anymore, certainly none with such an international reputation that the Russians would have heard of them. Most of the big names have died since the end of the Cold War.
Angelo Codevilla is an excellent choice as the American equivalent to Alexander Dugin, except it seems he lacked the influence within government for his ideas...if only more Republicans (including Trump) paid attention to what he was saying.
Of the other names you mentioned, Michel Houellebecq is the most interesting although its doubtful the Macron government pays attention to him.