https://github.com/DeterminateSystems/nix-installer I've had good experience with this installer if you have root access. I also installed nix on my work HPC cluster running Ubuntu via nix-portable.
This installer and the relationship between DetSys and Nix has also been subject to major criticism about conflict of interest between community interests and DetSys, since everyone agrees the official Nix installer has major issues. "Determinate Nix" (as DetSys calls the nix configured with their installer) also enables features that are the de-facto way to use Nix these days, but are disabled in the default distribution because of... let's say... commitment issues.
If you want a community run alternative, try Lix. They have a version of the DetSys installer too - and they actually cut releases of nix instead of building moats around it.
It's basically at the point where it just needs a redirect from the nixos.org domain, and for the project/community to work through how to manage its development/relationship to the Nix repo.
It's generally a response to corporate interests (including Anduril, who put Nix on autonomous weapons) and elbow-shoving so-called meritocracy (including a very infamous concern troll) becoming dominant inside the Nix community and Nix leadership, by people who didn't want to work from inside the system to reform, but also know they can't maintain all of Nixpkgs by themselves either (which already bled a bunch of maintainers).