Traceback (most recent call last):
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/application/application.py", line 62, in OnInit
self.plugin_loader.enable_plugins()
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/application/pluginloader.py", line 43, in enable_plugins
p.enable_on_startup()
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/application/pluginconnector.py", line 52, in enable_on_startup
self.enable()
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/application/pluginconnector.py", line 57, in enable
self._plugin.enable()
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/recentfiles/recentfiles.py", line 44, in enable
self._add_recent_files_to_menu()
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/recentfiles/recentfiles.py", line 114, in _add_recent_files_to_menu
self.register_action(action)
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/pluginapi/plugin.py", line 204, in register_action
action = self._frame.actions.register_action(action_info)
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/ui/mainframe.py", line 751, in register_action
self._menubar.register(action)
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/ui/actiontriggers.py", line 60, in register
menu.add_menu_item(action)
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/ui/actiontriggers.py", line 98, in add_menu_item
menu_item = self._construct_menu_item(action)
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/ui/actiontriggers.py", line 107, in _construct_menu_item
menu_item = self._create_menu_item(action)
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/ui/actiontriggers.py", line 139, in _create_menu_item
pos = action.get_insertion_index(self.wx_menu)
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/action/action.py", line 40, in get_insertion_index
return self._insertion_point.get_index(menu)
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/action/actioninfo.py", line 286, in get_index
index = self._find_position_in_menu(menu)
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/action/actioninfo.py", line 296, in _find_position_in_menu
if self._get_menu_item_name(item).lower() == self._item.lower():
File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/robotide/action/actioninfo.py", line 301, in _get_menu_item_name
return self._shortcut_remover.split(item.GetLabel())[0]
AttributeError: 'MenuItem' object has no attribute 'GetLabel'
OnInit returned false, exiting...
Error in atexit._run_exitfuncs:
wx._core.wxAssertionError: C++ assertion "GetEventHandler() == this" failed at /Users/robind/projects/bb2/dist-osx-py38/build/ext/wxWidgets/src/common/wincmn.cpp(475) in ~wxWindowBase(): any pushed event handlers must have been removed

Solution: 
python3.9 can install beta version
pip install -U –pre robotframework-ride
It will start normally after you had installed it.