Hard mode config files
Config files for normal and hard modes are found in \config-overrides\normal and \config-overrides\expert respectively.
To install hard mode, drag the files inside \config-overrides\expert into the main config folder, as below:
The same for reverting back to normal mode, plus manually deleting \config\globalgamerules.cfg to cancel forced peaceful.
Windows users may also use pack-mode-switcher.bat found in the root directory. (It was here so it comes with the pack, but curseforge clearly doesn't want suspicious file in the release.')