I want to clarify some things:
The old software center (solus-sc) and the new software centers ( gnome-software and discover) works different fundamentally. The old software center calls eopkg directly, so it will list whatever we have in the repository. The new software centers doesn't call eopkg directly, it is using a layer called packagekit. packagekit itself can list all the software we have in the repository, but the new software centers also relies on appstream metainfo to display information about the package.
Sometimes a package doesn't bundle its own AppStream metainfo and the we have to add it ourselves. I already explained this a few times, read more about it here. One of the biggest offender of not shipping its own AppStream metainfo are CLI/terminal apps which is understandable because you use it on terminal, why not install it via terminal too?
Now, if anyone want to be part of the solution. Please help us with this issue. There is a step by step instruction there to guide you. There are 130 packages left without the AppStream metainfo and that is not counting the CLI/terminal apps we are ignoring for now. I have been doing this by myself for the best part of two years and frankly I am tired.
Please, for the love of god if you want all applications, all apps, all packages show up in the software centers, help us. Or write the a new software center, not for eopkg but for moss, so we drop the need for packagekit and appstream in the future. That is all.