The problem is, container (or immutable) based development environment, like DevContainers and Nix Flakes, still aren't the popular choice for most developments.

I self-hosted DevPods and Coder, but it is quite tedious to do so. I'm experimenting with Eclipse Che now, I'm quite satisfied with it, except it is hard to setup (you need a K8S cluster attached to a OIDC endpoint for authentication and authorization, and a git forge for credentials), and the fact that I cannot run real web-version of VSCode (it looks like VSCode but IIRC it is a Monaco fork that looks almost like VSCode one-to-one but not exactly it) and most extensions on it (and thus limited to OpenVSIX) is a dealbreaker. But in exchange I have a pure K8S based development lifecycle, all my dev environment lives on K8S (including temporary port forwarding -- I have wildcard DNS setup for that), so all my work lives on K8S.

Maybe I could combine a few more open source projects together to make a product.