After watching a presentation by Holger Vogt in a Youtube video FOSDEM 2024 - ngspice circuit simulator stand alone and embedded into kicad, I located the source of the examples in a forum post More simulation examples for KiCad/Eeschema/ngspice.
To make it easier to play with the examples (and update/maintain them), I have migrated the examples from the forum post (extracted 7z archives and documentation) to this GitHub repository: https://github.com/labtroll/KiCad-Simulations
To run any of the 34 simulation examples, simply clone, fork or download the repository and open any of the contained *.kicad_pro or '*.kicad_schfiles and from theSchematic Editor: Inspect>Simulator>Run` (green triangle).
Disclaimer I have not verified the simulation examples, and they are supplied as-is, but feel free to propose changes/additions by creating issues and/or pull requests.