Comment 9 for bug 1579415

Synaptic and Muon look at packages, which is something different than applications.
Applications and software with much metadata is in a different file. We generate the data from packages, but it is not the same as a package. In order to get enough metadata out, the packages must match some criteria, and meeting those is the job of the individual package maintainers.
So, your bug against gnome-software is actually a bug against Krita, bug #1576827 in particular.

Since samba is a technical thing, it will likely never be shown in a tool like GNOME Software, instead it will be installed in an app actually wants it.

3rd-party repos not being able to display apps is another, different bug, bug#1576780

So, yeah, that's the whole story. Maybe this issue can be closed in GS as invalid.

The "nobody cared enough" statement was basically me being frustrated with not enough people caring to fix their metadata, something which will improve in future, fortunately.
(We will also have more visible diagnostic messages in Debian soon, which should help fixing this issue. See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=806740 )