I noticed the hash table implementation in _jit_data. As GNU lightning is now shipping with Gnulib and Gnulib has a well-maintained hash module (see gnulib/lib/hash.h), it can make sense to simplify long-term maintenance to remove the ad hoc-code of lightning and call Gnulib code instead.
This is, for sure, nothing that is pressing. And there is probably a lot of other, especially configuration and detection code, that is still doubled between lightning and Gnulib.