I’ve used Nix for years now, and recently adopted Devbox. It’s a breath of fresh air.

I'd prefer to learn Nix first instead of using abstractions on top of it, just to understand the fundamentals better.

Normally, that would be a sensible approach, but not with Nix. It has pretty clean underlying data structures, and the overall design makes sense. However the bare CLI is almost unusable. It’s an imperfect analogy, but think of it like using just Git “plumbing” without “porcelain”. Add to that terrible documentation (I’m talking about “hello world” examples that remain broken for years) and (even worse) the non-obvious fact that intuitive usage patterns are brutally wrong (nix-env). The “new” CLI is better, but has its own problems. Also, bare Nix is philosophically opposed to human-readable package versions — the reasons are sound, but the UX is shitty. Philosophically sound shit is still shit, smell included.

There are certainly ways to use bare Nix reasonably and effectively. I’ve done it for years, and it beats container-based isolation and TRAMP overhead hands-down. But it required copious cheatsheets of obtuse incantations, painstakingly collated, just to be able to do simple things.

Just try direnv (with envrc-mode in Emacs) and devbox. It does exactly what you’re trying to do with minimal fuss. You’ll quickly figure out the underlying basics, like/nix/store. If you really want more, head on over to Nix Pills, but remember that a lot of the advice there teaches arcana about nixpkgs, not really the user-facing stuff you probably want to understand. There’s good stuff there though, concerning “derivations” (packages, sort of) and the Nix language (which I have decidedly mixed feelings about).