So it's kind of like machine configuration as code, with Nix doing the heavy lifting. That sounds interesting. However, I wonder how it deals with scenarios like using "flox pull" to do an initial setup, then manually installing something, then months later trying to reconcile what the code says should be installed and what's actually installed.
Have you used Nix? As far as I know, you can't manually install something, at all. You need to add it to the Nix config for it to go in the environment.
My impression of Nix on Mac is that it doesn't have exclusive control of your system, so it would be possible to install something outside of its control loop.