It's Gonna Be A Long Knight

Normal sudoku rules apply. In cages, digits must sum to the small clue in the top left corner of the cage. Digits may not repeat along each of the marked diagonals. Cells separated by a “taxicab” distance of 4 may not contain the same digit. A “taxicab” distance from cell A to B is the minimum possible distance from cell A to cell B when traversed only through orthogonal cells. In other words, if two cells are H horizontal moves and V vertical moves from each other, their taxicab distance from one another is H+V.

try it here

Watch a solve from Simon Anthony here