As a grid manager myself I completely agree with @mjlbach that asking a beleaguered administrator to manage Nix installations across hundreds of machines is a very hard sell. I’d also agree with @teh that it takes the strongest of Nix advocates to provide the leadership required to successfully introduce Nix-based workflows into an organization.
I would surely have given up on Nix myself if not for the promise of correctness, hermetic reproducible builds, and the incredibly vast and fresh set of curated build expressions in the Nixpkgs collection. We created flox with the express goals of managing Nix at scale and lowering the adoption barrier for Nix in an enterprise setting, and for us it has addressed most of the issues raised in this thread. (Thanks @JosW for making the connection!)
We’re really interested to see how what we’ve built can be of use in other HPC environments, and to that end I’d invite everyone to sign up for our open beta and give it a go.