I don't know how you did this. Was it a fall, or a crash, or a jump? Is the frame still aligned? Can the crack be closed by manipulating the frame?
My fix would be to remove the crank and inspect the bottom bracket. If all was OK and aligned properly I would strip and burnish the area clean then "Alumaweld" a triangular 3mm thick 80mm x 80mm x 80mm aluminum wedge into the area and ride on.
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No matter where you're at... There you are... Δf:=f(1/2)-f(-1/2)