_tkinter now builds and links with non-system Tcl and Tk frameworks if they are installed in /Library/Frameworks as had been the case on older releases of macOS. If a macOS SDK is explicitly configured, by using ./configure --enable-universalsdk= or -isysroot, only a Library/Frameworks directory in the SDK itself is searched. The default behavior can still be overridden with configure --with-tcltk-includes and --with-tcltk-libs.