> Or something that works with PyPI directly

Poetry is python specific and does not solve the problems that pip/pypi has with native C/C++/Rust/etc modules.

Nix/guix solves all of that

Indeed. We have some Python modules written in Rust. It needs Rust nightly, because pyo3 requires Rust nightly. The Rust crate relies on libtensorflow. Unit tests for the Python module use Python and pytest. And we use our own build of libtensorflow (optimizations for AVX and FMA).

The dependencies of such projects are easy to specify in Nix. Moreover, it's easy to reproduce the environment across machines by pinning nixpkgs to a specific version.

I installed Nix operating system on an old lap top earlier this year, and indeed it does solve a lot of development and devops problems. I retired this spring, so I only played with Nix out of curiosity, but if I still had an active career as a developer I would use Nix.