The closest equivalent to the nixos ISO builder and reproducibility related to it in the fedora ecosystem is osbuild / imagebuilder - https://www.osbuild.org/guides/introduction.html

Imagebuilder claims reproducibility, but as far as I know it mostly installed rpm packages as binaries, not from source, so it's not really proper reproducibility unless all the input packages are also reproducible.

If the descriptions of building packages from source, building distro images, and reproducibility in the linked thread didn't make sense to you, you're probably not really the target audience anyway.

Nix is a declarative OS, where you describe what the OS should look like, instead of Ansible where you give the OS steps to follow. Silverblue and Nix are orthogonal aside from being Linux distributions--Silverblue is attempting to change how software is delivered using only containers on an immutable host.

If you're interested in an Ansible alternative that uses Jsonnet and state tracking to somewhat mimic Nix, check out Etcha: https://etcha.dev

Ansible makes mutable changes to the OS, task by task.

Nix is immutable. A new change is made entirely new, and only after the build is successful, all packages are "symlinked" to the current system.

Fedora Silverblue is based on ostree [1]. It works similarly like git, but on your root tree. But it requires you to reboot the whole system for the changes to take effect. Since Nix is just symlinked packages, you don't need to reboot the system.

More detailed explanation here [2].

[1]: https://github.com/ostreedev/ostree

[2]: https://dataswamp.org/~solene/2023-07-12-intro-to-immutable-...