Useful one to have appear in your inbox in the morning. Have just done this on a server, so I thought I'd put it here to remind myself. This works for debian and Ubuntu variants, which have the apt command (a meta-script for the apt-get ecosystem)
In note form …
Add the following text to /etc/logwatch/scripts/services/apt
#!/bin/bash /usr/bin/apt list --upgradable
Add the following text to /etc/logwatch/conf/services/apt.conf
# The title shown in the report. Title = "Packages to upgrade" # The name of the log file group (file name). # e.g for /etc/logwatch/conf/logfiles/apt.conf, we'd have Logfile = apt LogFile = NONE
As we have NONE there, we don't need to create /etc/logwatch/conf/logfiles/apt.conf.