How do I permanently turn off updates? Every night my MacBook turns off and updates.

I've switched off every System Preference I can find but still, if I go to sleep and come back, it's either trying to restart on account of the Software Update and an app which has an unsaved state is blocking it, or it's off.

What can I do to disable any and every Software Update attempt?
If you open the App Store and under the App Store menu item click on preferences. This opens a panel where you can change or turn off updates. This is for High Sierra. It may be different in Catalina but I thought it was worth the effort to check.