While NixOS goes a bit further with it, most other distrubtions also compile everything from source, cryptographically verify that the sources they use are not

While NixOS goes a bit further with it, most other distrubtions also compile everything from source, cryptographically verify that the sources they use are not tampered with, and have versioned dependencies between packages. Debian also has reproducible builds. The problem is just that the build systems did not strip pre-compiled object files before building from source. Even with that fixed, if nobody checks the source code then you can add all the backdoors you want, and there is nothing in NixOS or any other distro that would protect against that.