I don’t get NixOS

It’s not for everyone. The idea is to have your entire system reproducible with a few configuration files, which you’d then ideally store in a VCS like git.

I haven’t messed with it, but there is something appealing about the ability to reboot to an older snapshot of the system if an update breaks something, or being able to use a config file to restore your system to the exact OS version and exact versions of whatever apps you use.

They prefer the term “Jersey Classic”