I tried Nix a few days ago. I set it up on an existing Arch install. I installed a couple of packages with "nix-env -i [package] and then tried to update them with "nix-env -u" as instructed in the official documentation: https://nixos.org/manual/nix/stable/#ch-basic-package-mgmt
This ended up breaking the entire install. After a few hours of troubleshooting I found that the reason it broke was that it updated itself from version "nix-2.3.10" to "nix-2.3.10-x86_64-unknown-linux-musl" because it saw that package's version string as a version bump. The suggestion in the github issue was to instead use an unofficial third party package for basic package management because this was a known, long-standing issue that is not likely to be fixed.
This ended up breaking the entire install. After a few hours of troubleshooting I found that the reason it broke was that it updated itself from version "nix-2.3.10" to "nix-2.3.10-x86_64-unknown-linux-musl" because it saw that package's version string as a version bump. The suggestion in the github issue was to instead use an unofficial third party package for basic package management because this was a known, long-standing issue that is not likely to be fixed.
https://github.com/NixOS/nixpkgs/issues/118481
The experience came across as a massive red flag and I decided not to pursue it further.