I just ran a clean install on a M1 MacBook Pro, Big Sur, (macOS 11.1).
ffmpeg required a separate install (
conda install ffmpeg)
time pythonw testscript.py 565.57s user 186.21s system 274% cpu 4:33.95 total
It ran without a hitch. I then opened the test project in the GUI, and labeled frames, to make sure all the different GUIs worked. Other than having to drag to resize the main GUI to see all the buttons, everything I tested worked flawlessly.