答案1
You will find that with Catalina Apple has changed naming conventions and "Enhanced Dictation" is no longer something that is turned on/off in that way.
According to this KB article https://support.apple.com/en-us/HT210539
macOS Catalina introduces Voice Control, a new way to fully control your Mac entirely with your voice. Voice Control uses the Siri speech-recognition engine to improve on the Enhanced Dictation feature available in earlier versions of macOS.
It seems the procedure starts in System Preferences > Accessibility > Voice Control. And is Apple's "replacement' for "Enhanced Dictation."