[jolux]

Emacs mostly has problems with external language servers because its plugin model is archaic and brittle to a large extent compared to that of say VS Code. It's also far more flexible but with power comes responsibility, and I've found Emacs extensions far more likely to interfere with each other than in less composable editors. You don't need Nix to fix this problem.

[tikhonj]

Nix would help pull in the right versions of all the external non-Emacs packages you would need for a real IDE experience. Almost all the issues I've had with Emacs plugins have boiled down to poor interactions between Emacs and external software (wrong versions, wrong paths... etc), and Nix could fix basically all of it.

As a bonus, using Nix to manage Emacs dependencies would also give me full control over exactly which version of each package to pull in. This would create much more of a "distro" experience without needing any extra infrastructure.

[Geminidog]

Given the brittleness there should be at least a single configuration that works. I believe that tikhonj is right in the sense that nix can capture this configuration. Nix is not required but I can see how it can help.

[rgoulter]

Nix would be useful for a description of the non-Emacs dependencies. Particular versions of the compiler and LSP program. -- Some languages are more fickle about this than others.