Well, Nix has NUR which is a direct equivalent but it's not nearly as broadly used and I assume "here's a PKGBUILD for folks" is already too permissive for you if you're asking.
There's no maintainer vetting process in nixpkgs as far as I know, anyone can own a bunch of packages. There are quality standards and it's not "here's a bunch of nix code for folks" but it's the next possible thing in the line after that.
It seems like you may have mistakenly inferred that I have issues with the AUR?
I don't; I use Arch on 100% of my personal servers, have done so for something approaching 20 years, and don't see myself changing.
But I treat the AUR for what it is: a place where anybody can say "here's a PKGBUILD for folks" and it's on me to evaluate it on its merits.
I was legitimately asking the person upthread what other distro they felt had a better model for this kind of sharing, because they seemed to think this was a reason for Arch users to jump ship and I was curious what they thought would be the elements of a better system.
The NUR was sort of convenient before flakes were a thing, but now that there's a really common convention for sharing Nix code few use it. I bet most people who came across Nix in the last 4 years have never even heard of it.