The letter "d" is randomly added to text while typing.
When in an application that uses text. My Imac is randomly typing the letter "d".
I have changed keyboards.
I have left the keyboards turned off (wireless).
Further, when I am not in an application that allows typing, the iMac randomly plays the "basso" sound (this is the notification alert sound set in the sound preferences)
Mid 2017 27inch iMac: Catalina 10.15.7
iMac 27″ 5K, macOS 10.15