I have similar problems.
When I type netgen in the terminal under MacOS, there is some error:
dyld: Library not loaded: /Library/Frameworks/Python.framework/Versions/3.8/Python
Referenced from: /Applications/Netgen.app/Contents/MacOS/netgen
Reason: image not found
[1] 73123 abort netgen
When I type which python3, it comes:
/usr/local/bin/python3