Tcl Source Code

Built and installed tcl8.6.16 on macOS Monterey.
Then tried to build tk8.6.16:
% tar -xzf tk8.6.16-src.tar.gz
% cd tk8.6.16/unix
% ./configure --prefix=/usr/local/tcl8.6.16 --with-tcl=/usr/local/tcl8.6.16/lib --enable-framework --enable-aqua
% make -j8
% sudo make install
.
.
.
application-specific initialization failed: Can't find a usable init.tcl in the following directories: 
    /usr/local/lib/tcl8.6 /usr/local/lib/tcl8.6 /usr/lib/tcl8.6 /usr/local/library /usr/library /usr/tcl8.6.6/library /tcl8.6.6/library



This probably means that Tcl wasn't installed properly.

using Tk source directory tk9.0.2
verbose messages are off
scanning section Tk Applications
.
scanning section Tk Commands, version 9.0.2
shuffling ttk_widget.n to front of processing queue
shuffling options.n to front of processing queue
.........................................................................................
scanning section Tk C API, version 9.0.2
.......................................................................................
Assembling index
Rescanning 177 pages to build cross links and write out
.................................................................................................................................................................................
Done

After installing tcl 8.6.16, did you try running the installed tclsh 8.6.16 and see the "Tcl wasn't installed properly error"? Or are you seeing the error only on the Tk build?