How does Nix manage SystemD modules on a non-NixOS?

[toraritte]

Created this topic because there is a huge amount of information in the above thread, compared to what I was able to find on this forum:

• Packaging a dynamic website
• Configuring nix package by using nixos modules on non-NixOs system
• How to use nixos systemd user service definiton in non-nixos system via home manager?
• Systemd backend or “using NixOps to manage Ubuntu”
• Replacing Docker workflow for service ops with Nix