Ren'Py game files are platform agnostic. So download the PC version, unzip, copy the folder called game, then delve into the older Mac app (right click, show package contents, navigate to /Contents/Resources/autoplay), replace the game folder with the one you copied from the PC version.
Caveat: check if the Ren'Py version is the same: Script-version.txt in said game folder. If not, you're better off by building a Mac port yourself with the Ren'Py SDK.
Precaution: always make a duplicate of the old app before you start modifying it.
This usually works in other games but for some reason it's not working for this one. I replaced the game folder of the mac version with the game folder of the pc version, and the renpy versions are both (8,0,1). Any thoughts?
Here's the error that opens when I try to load the game:
I'm sorry, but an uncaught exception occurred.
Before loading the script.
ValueError: unsupported pickle protocol: 5
-- Full Traceback ------------------------------------------------------------
Full traceback:
File "/private/var/folders/k1/bc1nd1hs5zx32n5x2f910m200000gn/T/AppTranslocation/3AD494F0-D1AA-429E-8AAA-A52C7304C993/d/GatesMotel.app/Contents/Resources/autorun/renpy/bootstrap.py", line 316, in bootstrap
renpy.main.main()
File "/private/var/folders/k1/bc1nd1hs5zx32n5x2f910m200000gn/T/AppTranslocation/3AD494F0-D1AA-429E-8AAA-A52C7304C993/d/GatesMotel.app/Contents/Resources/autorun/renpy/main.py", line 357, in main
renpy.loader.index_archives()
File "/private/var/folders/k1/bc1nd1hs5zx32n5x2f910m200000gn/T/AppTranslocation/3AD494F0-D1AA-429E-8AAA-A52C7304C993/d/GatesMotel.app/Contents/Resources/autorun/renpy/loader.py", line 136, in index_archives
index = loads(f.read().decode("zlib"))
File "/home/tom/ab/x64lucid-deps/install/lib/python2.7/pickle.py", line 1382, in loads
File "/home/tom/ab/x64lucid-deps/install/lib/python2.7/pickle.py", line 858, in load
File "/home/tom/ab/x64lucid-deps/install/lib/python2.7/pickle.py", line 886, in load_proto
ValueError: unsupported pickle protocol: 5
Darwin-22.2.0-x86_64-i386-64bit
Ren'Py 7.3.5.606
Wed Jan 18 19:52:45 2023