Before investing more time into it I wonder whether the use of 'libfaketime' would be a valid solution for creating reproducible builds. According to 'pkgs.org' it is available for most GNU/Linux distributions; it is also part of both MacPorts and Homebrew.
https://github.com/wolfcw/libfaketime The idea is to do the following: export LD_PRELOAD=/usr/local/lib/libfaketime.so.1 export FAKETIME="2020-12-24 00:00:00" make all make doc This freezes the current time at a given value. On my GNU/Linux machine, this works out of the box: Together with MR !563, all PDFs are indentical for different builds, except for `/ID` values found in some (but not all) PDF files. Ghostscript apparently inserts random values, which are not based on MD5 sums or the like. Documentation files like 'notation.pdf', however, are completely identical. On the other hand, there is still some randomness in the lilypond build infrastructure (especially with the XML test suite and `essay.pdf`) that I have to investigate further. Werner
