I think the issue is - for macos, you must run the game executable directly from within the game directory.
As in:
- unzip the-underworlder-macos.gz
- cd libtcod-vcpkg-template-v0.0-3-gc8feb98-macos.arm64
- chmod +x ./the-underworlder
- ./the-underworlder
Sorry for the inconvenience.