For build instructions, there is: https://github.com/ankitects/anki/blob/ab6877c714f2930d7552cdd4c57e725047e7e80c/docs/new-platform.md and https://github.com/ankitects/anki/blob/ab6877c714f2930d7552cdd4c57e725047e7e80c/docs/linux.md.
The derivation probably needs a rewrite from scratch using buildBazelPackage. And maybe anki.pylib can get its own output to keep the closure of ankisyncd small…
Or should we just drop the source build in favour of anki-bin?