command-not-found works [1], however is showing that warning.
WARNING:root:could not open file ‘/etc/apt/sources.list’
Whonix does not ship /etc/apt/sources.list but only files in /etc/apt/sources.list.d/ drop-in folder.
( GitHub - Kicksecure/anon-apt-sources-list: /etc/apt/sources.list.d/debian.list for Security-Focused Linux Distributions )
That is because file /etc/apt/sources.list managed by a package could conflict with local users, causing interactive dpkg config resolution dialog.
Considering to apply the following workaround.
sudo touch /etc/apt/sources.list
sudo chmod o+r /etc/apt/sources.list
The latter command required due to umask hardening. (change default umask)
Any reason against creating an empty /etc/apt/sources.list which is not managed by any package?
[1] Well, perhaps except from requriing another workaround which breaks it, see this post: change default umask - #45 by Patrick.