DCAT-AP is, possibly, the most relevant standard of a catalogue of datasets (even resources as well). A data spaces’ data models’ building block needs a semantic catalogue of resources in DCAT-AP format.
You just connect to this URL and you can get it. It will be updated once a day and whenever a data model is published.
You can also reach it at home -> tools -> DCAT-AP catalog (last option)
As long as the catalogue and its structure can be enriched I’d like to hear from you any comments / additions and critics you wish / need at firstname.lastname@example.org
So you can enrich it before the official release