`flox` needs Nix to function. So the rpm/dev/OSX installers first install Nix, and then installs flox itself.

If you have Nix already, you can try it out as described here: https://flox.dev/docs/install-flox/#install-with-existing-ni....

side-note: with further improvements to Nix as a library, it may be possible to make installing Nix not necessary for flox to function, but this is on a longer time horizon... don't hold your breath