I too would like to know. One recommendation I saw in regards to learning to hack stuff like the Nintendo Switch is, first learn to write a kernel, and also learn about compilers. Also, personally I've been considering working through Bunnie Huang's "Hacking the Xbox".
Just finished reading "Hacking the Xbox," per your suggestion - agree that it's quite good at explaining the process. The actual presentation does a good job of condensing what I imagine was an arduous adventure. Thanks for the recommendation.