Comment 18 for bug 1548933

Nope, you don't need appstream-util at all, simply because there is no cache GS is reading from - GS is always parsing the data directly and creating an in-memory cache.

However, there is some setup needed for GS to work, and there is a cache which some apps consume instead of the raw data. Those are updated via `appstreamcli refresh`, which is exactly what you did when running `àpt update`, since an apt-update will trigger that.
Looks like for some reason your data was broken or out of date, I unfortunately have no idea how that could happen, unless APT screwed up or someone deleted the previous files in the cache and metadata locations.