I tried Debian + Nix once upon a time too. Honestly flatpaks and containers did everything I needed and more, and every dev team I’ve been on already has familiarity with the container workflow.
I’m a huge fan of Debian and Nix, don’t get me wrong, but it was shy of perfect for my use case. Glad it works for you though! I’ve been using Fedora + Nix home-manager with flakes for almost two years and I don’t think I’ll ever go back