I’m going nuts here… Ubuntu keeps talking to me, although I have uninstalled orca (via software center), disabled the use of “assistance technologies”. It still keeps talking!! Can anybody help?!
Go to the “Control Center” and under Hardware check the “Keyboard shortcuts” option and see what key is assigned to “Toggle Screen Reader”.
In my computer is: Alt+Mod4+S but I changed to Alt+Ctrl+Shift+S because I don’t now where the Mod4 key is 
Then press that key (Alt+Ctrl+Shift+S in my case).
EDIT: Mod4 is the right-windows key.
Try to uninstall orca via terminal:
sudo apt purge gnome-orca
thank You so much for Your help!! Because of some other issue I did a rollback with timeshift anyway, but next time orca bugs me I’ll know how to shut him up…