gnome-software does "apt update" even if download-updates=false
I have made sure that nothing on my system does an "apt-get update". But when gnome-software is installed, then I find that updates are known about when I do an "apt-get dist-upgrade". Removing gnome-software fixes the problem. I don't want periodic checks for updates to use up my very limited bandwidth. (Ubuntu 20.04, gnome-software 3.36.0)
Edited by jstnlth