I guess this isn’t technically the engine, but it is part of the build process…
Do we have a solution for generating the PDF files (guides mainly) at this time? The original build system used wkhtmltopdf but that has not been maintained in many years. I found an open source program that may work if we don’t already have a solution: weasyprint. It can be installed with brew (it has a ton of dependencies).
I’m in the process of going back to the original open source repo trying to figure out how to properly generate the documentation so we can restore it to the project. The buildbot.mk file got dropped at some point along the way but the scripts is uses still seem to be available.