It does not matter what Wikipedia says Lovecraft spelled it "Cthulhu" as did all of the original members of the Lovecraft Circle, Clark Ashton Smith, Robert E. Howard, Robert Bloch, Frank Belknap Long, and Henry Kuttner. and, to some extent, August
Derelth. I think that these provide bona fides for the spelling "Cthulhu". All else, in my opinion, is vulgarity.