A friend of mine has a Mid 2012 MacBook Air running Catalina, and he's trying to get the Android emulator BlueStacks running on it. He gets an error saying
System extension blocked.
Enable the extension from Security & Privacy System Preferences pane by clicking 'Allow' button and BlueStacks will launch again.
I looked in that pane, and couldn't find anything like that. I'm obviously missing something here but I don't know what!
A screenshot of the error is attached: