This probably goes against the flow, but I tried NixOS on a VPS and I found the tools to be inscrutable. Was so confused about Nix packaging and whether to use Flakes.
1. The purist: Is on an actual crusade to promote Nix and stomp out any competition, because, "reproducible."
2. The enthusiast: Likes using Nix to speed up development but recognizes it has a ton of shortcomings, among others being not friendly to beginners, and tends to avoid using it in production critical stuff.
3. The ex-Nix: matches the enthusiasm of the purist in stomping out Nix wherever possible and actively promoting its demise.
I'm personally in the second category. I use Nixos for my main development machine and really like devshells. Beyond that, I try to avoid it as much as possible for production.
I have no experience running it in production, but I imagine if you don’t want to use containers it’d be a pretty good option.