We already have a warning about Tk versions on macOS, see macosx.tkVersionWarning().  It is currently printed in new shell windows.    It would be straightforward to add warnings when using anything other than 8.5.18 or 8.6.8+.  I suggest this approach.

As for the docs, IMO we should update the "GUI Programming on the Mac" section of https://docs.python.org/3/using/mac.html; I'll prepare a PR.


I also suggest updating https://www.python.org/download/mac/tcltk/. The following two current paragraphs should be improved:

"If you are using Python (prior to 3.7) from a python.org 64-bit/32-bit Python installer for macOS 10.6 and later, you should only use IDLE or tkinter with an updated third-party Tcl/Tk 8.5 (not 8.6), like ActiveTcl 8.5 installed."

"If you are using macOS 10.7 or later, the Apple-supplied Tcl/Tk 8.5 still has serious bugs that can cause application crashes. If you wish to use IDLE or Tkinter, install and use a newer version of Python and of Tcl/Tk."

I'm happy to suggest clearer wording; I'm not sure where to post a patch/PR, though.