Haven’t actually deployed to k8s, currently using them to isolate local development but there I know (at least at one point) kubernetes supported other images than just docker images but even if they do t NixOS containers supports generating docker images...

I imaging a ci/cd flow where it build the image and installs your app via a local Nix package built from source in your git repo and all that needs to be shared is the git repo and you have everything you need to reproduce the container er running in production.