As I wrote already in the readme, if you scroll up you can see it under "requirements", the ZX Spectrum version is intended to run on real hardware with a divMMC device. You have to put all the files from the archive onto the SD card of the divMMC device. It loads the pictures from the SD while executing the .TAP file. If you really want to play Rabenstein with emulation, Fuse at least allows simulating a divMMC environment. There are quite a few tutorials out in the wild that explain how you can do that. Hope this helps!