py 2's tkinter breaks because it assumes "10." as the first version identifier - so it bails assuming you're running 10.0 or 10.0.1
Thank you I was able to make changesSeems to be an issue with Big Sur and python.
From CorpNewt:
Download and install Python 3.9 from here, https://www.python.org/ftp/python/3.9.0/python-3.9.0-macosx10.9.pkg
When installed run this compiled version of ProperTree to use python3