This looks interesting. But I’m not sure I understand the full implications of it. Using this on macos, should I see it as a replacement of homebrew, sort of? Or does if do much more? Can I install and run something like i3 on macos using this?

It would be like installing nix or flatpak beside a the distro’s default package manager.
Could potentially be installed anywhere… such as on android if a user prefers it over the native package manager.