Per the documentation you have to provide dumps of the original Xbox bootroms, and it can optionally use a HDD image taken from a real Xbox, but the latter isn't required because they provide a basic cleanroom reimplementation of the dashboard you can use instead.
The CPU in the Xbox was literally an off-the-shelf Intel processor (some crazy people even soldered in faster CPUs that were never meant for the Xbox) but as I understand it the GPU is weird, and that's where most of the difficulty with emulation comes from. It's a unique mashup of GeForce 2 and GeForce 3 IP that was never used anywhere else, so the existing efforts to reverse engineer GF2 and GF3 for Linux drivers were of limited use.
https://xemu.app/docs/required-files/
The CPU in the Xbox was literally an off-the-shelf Intel processor (some crazy people even soldered in faster CPUs that were never meant for the Xbox) but as I understand it the GPU is weird, and that's where most of the difficulty with emulation comes from. It's a unique mashup of GeForce 2 and GeForce 3 IP that was never used anywhere else, so the existing efforts to reverse engineer GF2 and GF3 for Linux drivers were of limited use.