https://bugzilla.redhat.com/show_bug.cgi?id=1823599
--- Comment #14 from Miro Hrončok mhroncok@redhat.com --- When the software repositories are created, the contents of those file are scrapped/loaded to a central place and than offered as metadata for e.g. GNOME software.
You could probably somehow reproduce locally (although I have never actually tried this and the instructions are not complete):
1. put the built rpms into an empty directory 2. run createrpo over them to create a DNF repository 3. run appstream-builder to extract the appdata 4. run modifyrepo to merge the appdata to the repo metadata 5. add a repo file to your system with file:// URL 6. see GNOME software
However, I don't know all the command line options and switches to use. There is an easier way. Build the package in https://copr.fedorainfracloud.org/ -> it will give you a repository with appdata.