For future reference, into the Cc field, you should place the maintainer's email address or GitHub handle. You can find this information by running the command port info --maintainers [portname]. Don't literally paste that command into the Cc field. Also, remember to use WikiFormatting when writing in Trac.
Since the unknown symbol was referenced from a sundials2 library, I think this is probably a bug in the sundials2 port rather than the cantera port. The cantera source code does not contain the string klu_solve but the sundials2 source code does.
I don't know if it has any bearing on the problem, but I'm suspicious of the use of the flat namespace, which has not been recommended for over a decade. I don't yet see where in the build system the flat namespace is being requested.
I notice that the sundials libraries are being built with -undefined dynamic_lookup, which means that if there are any undefined symbols at build time, it doesn't complain about them, assuming that they will exist at runtime; in the case of klu_solve at least, that's apparently not happening. If I remove that flag from the build, then the build fails with undefined symbols errors, not unsurprisingly.
