Something I wonder about after reading your overview - software from outwith the package manager. It's quite often that the package manager in the Linux distro

Something I wonder about after reading your overview - software from outwith the package manager. It's quite often that the package manager in the Linux distro I'm using has an old version of Nginx, PHP, or whatever, and so I have to build my own, or at least use an alternative package source. How is this kind of thing handled with NixOS config? (if it is)