This is what I get:
<module 'objc' from '/Users/baptisteguesnon/Library/Application Support/Glyphs 3/Repositories/GlyphsPythonPlugin/Python.framework/Versions/3.9/lib/python3.9/site-packages/objc/__init__.py'>
This is with the glyphs python. Can you switch to the python version that you used before? You can switch it in Preferences > Addons.
Oh then it’s the screenshot that I uploaded in my first answer:
Traceback (most recent call last):
File "<internal>", line 4
File "GlyphsApp/GlyphsApp/__init__.py", line 642
AttributeError: Cannot replace selector 'font' in 'GSApplication' by non-selector`
<module 'objc' from '/usr/local/Cellar/python@3.10/3.10.4/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/objc/__init__.py'>
I also have 3.9.13 installed but it triggers the same error (pyobjc is also already insalled).
Ps. Sorry for my slow answers, for a reason I didn’t get any notification for your answers.
Can you remove all plugins and clear the Repositories folder. Then install python and some plugins from the Plugin Manager again.