It’s something we might see with the next EL release cycle. rpm-ostree has treefiles complete with the option for (experimental) lockfiles. There’s already config files for CentOS Stream to build CentOS Stream CoreOS, and those can be adapted for Alma. I think, atm, it’s more of an issue of general interest than technical limitations.
I've been messing about with NixOS for the past 2 weeks or so. While I think I know enough to plug in the right text in the right spots to get a system configured I feel like I understand nothing about the nix language and the syntax is extremely unintuitive to me. If another distro offered declarative configuration as well as something like Nix's options I would easily swap away from NixOS at this point.
I feel like I understand nothing about the nix language
Pure lazy unityped lambda calculus, basically a lazy lisp with records instead of lists. Or a pure, lazy, lua.
Pure is important because reproducibility, lazy is important to not have to evaluate all of nixpkgs before you can build anything, lambda calculus well it needs to be turing complete, support things like functions in in some way though TC is only used very, very very deep down in the system. They literally use the y-combinator to do recursion, like when bootstrapping stdenv.
The syntax is unintuitive, yes, but aside from the semicolon cancer actually not that bad. My biggest gripe with the language is it not having a proper type system, like you put a list where a string is expected or the other way around and you get five screenfuls of backtrace through the whole evaluation stack and due to laziness the actual location of the error might not even be in there.