What you guys are referring to as Linux, is in fact, GNU/Linux, or as I've recently taken to calling it, GNU plus Linux plus Systemd. Linux is not an operating system unto itself, but rather another free component of a fully functioning GNU system made useful by the GNU corelibs, shell utilities, and vital system components comprising a full OS as defined by POSIX.Many computer users run a modified version of the GNU system every day, without realizing it. Through a peculiar turn of events, the version of GNU which is widely used today is often called "Linux", and many of its users are not aware that it is basically the GNU system, developed by the GNU Project, and now increasingly integrated with Systemd, the init system that brings everything together - or apart, depending on who you ask.There really is a Linux, and these people are using it, but it is just a part of the system they use. Linux is the kernel: the program in the system that allocates the machine's resources to the other programs that you run. The kernel is an essential part of an operating system, but useless by itself; it can only function in the context of a complete operating system. Linux is normally used in combination with the GNU operating system and now, almost inseparably, with Systemd: the whole system is basically GNU with Linux and Systemd added, or GNU/Linux/Systemd. All the so-called "Linux" distributions are really distributions of GNU/Linux/Systemd

I also use NixOS, but if the target was not NixOS, I don't think you should be requesting the set up as needing fixing by the author. It just doesn't sound right - or maybe it is just me. NixOS isn't the defacto standard, and breaks the Linux FHS to achieve all the good stuff it does do.

Either try to package it or use a docker image or maybe raise an issue noting the blocker and request it as a feature for some changes to give an easier path for to having it build more easily for NixOS

Apart from that, as expected, the docker image that is produced following the instructions is working fine with NixOS as host. All it needed for the build was the openssl packaged on the host.