the Pd-tree of the 'regular' mac version differs from the ppc one.
it has a "frameworks" folder (with Tcl in it) that's not in the ppc one.
furthermore, it's unclear for me what exactly is part of the embedded
Wish implementation.
i tried replacing the whole tcl folder, to no avail.
Did you read the mac/README.txt? There really are "manuals" for most of this...
That explains the layout of the Pd.app and the Tcl/Tk requirements. The main issue of things is that for the longest time, macOS only came with Tcl/Tk 8.4 preinstalled. Later it came with a buggy version of 8.5 which we avoid by embedding a newer, better 8.5 version within the app bundle. This version is for newer intel macs and the ppc compatible build uses the older 8.4 provided by the system.
If you want, you can probably use the mac/tcltk-wish.sh script and set the --arch ppc flag to try and build for ppc specifically, but you will need to 1. have the 10.5 to 10.6 SDK available and 2. choose a version of Tcl/TK that will work on it. I mention #2 as I don't know if Tcl has dropped ppc support yet, perhaps not. A further option might be to find an old pre-compiled ActiveTCL download of 8.5 for ppc somewhere, install it on the machine, and update the Pd.app bundle with the wish for there, either using the mac/osx-app script or manually.
i n any case, check out the readme and you can use the scripts to automate building Tcl/Tk and the app bundle. It's all there, just not tested on such an old system.