I believe the whole reproducible-builds.org project started at Debian [0], the Core Team is still all made of Debian Developers, more information at: https://reproducible-builds.org/

Their documentation has some really good pointers at common issues and how to solve them: https://reproducible-builds.org/docs/

And the diffoscope tool is very useful for debugging.

[0] I believe other projects had similar things going on but the Debian one became the main to serve as an umbrella.