Ok, I have a fix for the library issue on older macOS versions... actually back ported from TK itself:
I will fold this in as a custom patch we apply when building the downloaded tarball, as before.
8.6.13 was released last November. Judging from the current development activity, there should be an 8.6.14 release fixing quite a number of macOS 14-related stuff.
It might make sense to put out a 0.54-1 bugfix release with 8.6.13 then follow up again with 8.6.14 when it comes out, either via 0.54-2 or 0.55-0.