Yesterday, while assessing a new client site, we ran across a technology we have not seen before: Sphinx Search. The site, while built in Drupal, had some very unusual techniques used to load Sphinx -- a previous developer had basically made a copy of the bootstrap.inc and hard-coded some autoload paths to load their custom Sphinx libraries.
To get the site to even load, I bundled up Sphinx in a Docker container, and copied over the configurations, language pack, and data. Then I had to debug until I found where the autoload path was hard-coded, deep inside a core vendor file. Problem solved! Our dev site now loads up just fine.