I know that a lot of what Nix does is working around its break from FHS, but I can imagine there are still things that seep through. Are there any unsolvable problems due to this?
I saw on this post that it is possible to use FHS on Nix. Does this solve all potential issues then?
Now you’ll have a zillion users trying to install software in ways that violate all the assumptions that NixOS operates on, but which are still tightly coupled to your NixOS config. Now updates to your system, or even seemingly unrelated config changes (through some transitive dependency chain) can easily break that software.
So now we’ve basically removed half the advantages that motivate Nix/OS in the first place, and when stuff breaks it will look like it’s Nix’s fault, even if it isn’t.
On the other hand, nixpkgs is already the most comprehensive repository of system software out there, and for 99% of packages Nixifying it is pretty trivial. Hell, my NixOS config does that for 3 different GitHub repos right inline in my config.nix