How can I completely stop automatic update checks in Ubuntu 19.04?

I have tried many suggestions and none of them works. I do not want my Ubuntu system to touch the network in any way to check for updates until I explicitly run an update check. I've set the control to "Never" in the GUI application with the repository. I've disabled each systemd timer which says a lot about the update. Yet, I get $ # @! update notification notifications popping up from time to time. What should I do to eradicate this scourge on Ubuntu 19.04?

Note that I do not want to simply disable the update-notify popup, I want to disable all network traffic while checking the update.