回答1
At first I tried:
sudo apt-get remove unattended-upgrades
But it was insufficient. I also had to do this:
sudo systemctl stop apt-daily.timer
sudo systemctl disable apt-daily.timer
sudo systemctl disable apt-daily.service
sudo systemctl daemon-reload
回答2
Just a supplementary, first you can list the task:
sudo systemctl list-timers
and find apt-daily-upgrade.timer, then disable it
sudo systemctl stop apt-daily-upgrade.timer
sudo systemctl disable apt-daily-upgrade.timer
sudo systemctl daemon-reload