Hi, Regarding a GUI tool for Nix, I think we may consider Nix and NixOS separately.
Considering NixOS, graphical tools can be interesting for beginners but this can be difficult to implement: we have to define a more standard way to install packages, implement a graphical installer for NixOS, implement a graphical package manager or integrate Nix in existing package managers (such as gnome-software-manager)… In addition, this should be compatible with our current workflow based on editing Nix files. Finally, it would also be nice to have a graphical tool for “per-project” configurations, which is, in my opinion, a killer feature of Nix for “normal” users (for example, to create a working Python environment without having to use virtualenv/conda/whatever).
On the other hand, I think it would be very beneficial to have a graphical tool for using Nix on other distributions than NixOS because it can solve widespread problems: let a normal user install software, install applications that are not in the distribution software repository. In fact, I’m quite tired of reading forum/chat/blog posts presenting snap/flatpak as a good solution while Nix is better on almost all points: more mature, more packages, better isolation/sharing, etc. The main drawback of Nix seems to be advertising…
Disclaimer: I’m the author of nix42b.