How to prevent Siri from sending messages on the Locked screen?
How to prevent Siri from sending messages on the Locked screen but still retain the ability to access Siri on the locked screen for other tasks?
iPhone 11
Settings/Siri & Search, turn off Suggestions on Lock Screen.
If you are asking about Notifications and not Siri Suggestions, go to Settings/Notifications and uncheck the Lock Screen setting for each of your apps.