Thanks for the report and the PR. Yes, detect_tkinter_darwin() had a number of problems due mainly to how Apple has first deprecated and more recently removed the option to have header files installed in the running system. Plus some nasty quirks of how the Tcl and Tk frameworks are built make it difficult to use them without hacks for embedding while supporting Python build options.  Your analysis was helpful. In the end, I tried to fix this and some more general problems in detect_tkinter_darwin() with PR 20171 for Issue34956 which will be available in 3.9.0b1.