Bending most fine art papers around corners is easy if you first glue the print to the major plane of the substrate, then brush a thin solution of glue in water over the still-exposed paper base wings from the back, let that soak in to soften the paper, then apply heavier glue also with a brush, let than get slightly tacky, and start wrapping. I'm simplifying just a little, but it works starting with your third attempt. Be sure to slightly sand down the sharp edges on the substrate before anything, but not as much as you see on canvas stretcher bars. If your print is varnished do this within a day or less of varnishing. Without the water softening step, it's cracks for sure.