NixOS is described as 'GNU/Linux distribution that aims to improve the state of the art in system configuration management. In existing distributions, actions such as upgrades are dangerous: upgrading a package can cause other packages to break, upgrading an entire system is much less' and is a popular Linux Distro in the os & utilities category. There are more than 100 alternatives to NixOS for a variety of platforms, including Linux, Self-Hosted, Mac, BSD and Windows apps. The best NixOS alternative is Linux Mint, which is both free and Open Source. Other great apps like NixOS are Ubuntu, Debian, Fedora and Arch Linux.
Manjaro is ironically less stable in practice than Arch. Its 1-2 week package hold "for stability" often breaks dependency sync with the AUR and causes unique bugs not found in Arch. Arch's true rolling model with synchronous updates is ultimately more reliable.