Nice and concise guide!

The reason that the Nightly binary will not run directly on NixOS is due to the fact that all NixPkgs binaries are hardcoded with a specific dynamic linker (as there can be multiple versions of glibc for different programs). Programs that expect the environment to provide a loader (say, at /lib64/ld-linux-x86-64.so.2) will fail out:

$ ./firefox
sh: ./firefox: No such file or directory

The differences in the binaries:

$ # Firefox Nightly from mozilla.org
$ ldd ./firefox  
        ...
        /lib64/ld-linux-x86-64.so.2 => ...

$ # NixPkgs Firefox
$ ldd /nix/store/ ... firefox-unwrapped-72.0.2/bin/.firefox-wrapped  
        ...
        /nix/store/ ... glibc-2.27/lib/ld-linux-x86-64.so.2 => ...

Solutions:

• patch the binary with the library paths yourself (maybe with autopatchelf)
• run the application in a FHS environment (maybe with steam-run)
• use a Nix overlay to acquire the appropriate package (this solution)
• compile it yourself