[QGIS-Developer] non-standard-library Python modules available to QGIS plugins

[Raphael Das Gupta]

Heya all

What Python modules (beyond the "qgis" module provided by QGIS itself 
and the ones built into the Python language or included in its standard 
library) can QGIS plugins expect to be accessible?

Or asked the other way around: When packaging QGIS (e.g. for a Linux 
distribution), what Python modules do I have to make available in its 
Python, so that plugins may use it?

While one could probably determine this by looking at existing packaging 
efforts, e.g. the dependencies of Ubuntu package "python3-qgis" from 
https://qgis.org/ubuntu-ltr, I wonder whether this isn't already 
documented somewhere, as this should be of interest for both plugin 
authors and application packagers.

My context: I'm trying to improve the QGIS experience on NixOS and other 
NixPkgs-based installations and would like to do that "right" rather 
than basing my changes on guesswork. I've collected my current findings 
on https://github.com/NixOS/nixpkgs/issues/59842

Kind regards,
Raphael