Remove PCB from metallic casing?

I’m disassembling an old and malfunctioning LG E2360V-PN monitor to see if I can fix it by replacing the capacitors. But, I was met with an unpleasant surprise: the PCB seems to be enclosed in a metallic casing, and I have no idea how to remove it!

I’ve already unscrewed all visible screws but it won’t budge. The bottom side of the metallic casing has a suspicious notch that seems to be holding it in place, but I’m not that sure what to do about it. I could always try to cut the metallic case, but I fear I’ll probably damage the board like that…

Bottom view with notch in red square:

Top view:

Any ideas/suggestions are welcome!