Software Updater wants to update Samba
apt list says that Samba is not installed.
$ apt list --installed samba
samba: Installed: (none)
...
Why does Software Updater want to install a package that is not installed?
All credit to Charles Green for this answer
Although I do not have Samba explicitly installed, I have another package installed that includes Samba.
This can be demonstrated using
$ apt list --installed "*samba*"
Or
$ apt-cache rdepends samba | grep " "|xargs apt list --installed
And there is a security update available for Samba, so Software Update wants to update Samba.